As someone who has taken the GMAT more times than you did, whose best score is lower than yours, and who will keep taking it no matter what until he reaches his target score, I believe I may have a thing or two to share with you.

In fact I echo your experience so much that I don't even know where to start LOL. I think it's pretty clear that you are capable of achieving your target score academically, plus there are way more experts in this forum who can help you in that regard than I could, so I'll speak more from a mental standpoint.
You titled this post saying GMAT is the biggest failure of your life, first I think you gave this little test called GMAT way too much credit, second, I think it might very well be quite the opposite. Not only GMAT might not be your biggest failure, this whole experience in fact might be your biggest asset when you look back, say, 10 years from now. You learn nothing from getting a perfect 800 on your very first try, but you can learn a ton lot more if you had to put in the time, the effort, and the struggle in getting the score you want. Like people always say, it's not about the result, it's about the journey. If it were so easy, why even bother doing it? What satisfaction or learning do you even get out of it? One well-known athlete once said, "If you don't go out there and put in the work and effort, one, you're not going to get the result, but two, and more importantly, even if you did, you don't deserve it!" So take this whole experience as an opportunity to hone your skills, both academically and mentally, as well as an opportunity to make yourself a stronger and better person. When you look back in many years you will probably be grateful what this journey has given to you.
With that being said, I want to start with - why give up? I personally have been preparing and taking the GMAT on and off for almost two years, I'm still far from getting my target score and not even to mention that my scores from the last two times that I took it have actually dropped by more than 100 points each compared to my best score which is from a year ago. So I think I'm in a more dire position than you are, yet in no way I am giving up. Being a graduate from the top 10 universities in the world for both my bachelor and masters degrees, I never really had any problems with exams or whatsoever growing up. But after being out of school for so many years and taking the GMAT for the first time, it has shattered my confidence constantly more than anything else did in the past 5 years. After my score dropped by more than 100 points, I was so devastated that I felt hopeless, helpless, defeated and thought about giving up. I told myself that maybe I'm just bad at GMAT, maybe those who got higher scores are just better than me, maybe I'm just not as good as I thought I am, maybe GMAT is something that I'll never be able to overcome in my life. But then, I don't even remember after how long, I came to the realization that if I give up like this, not only I would fail at GMAT, but more importantly I would fail myself. I will never be able to look at myself the same way ever again, I will regret for the rest of my life and probably take this regret with me to my grave. So I told myself that as long as I don't give up, one day, I will eventually come out on top. I don't care if it takes another year, another 3 years, or even 5 years, what difference does it really make after all? One can only be truly defeated by giving up, thus it is impossible to fail if you simply don't give up. As of now, I am ready to happily and rightfully use up all my 8 allotted times to take the GMAT if I have to, and maybe even find ways to continue taking it beyond the 8 times if I still haven't reached my target score by then. After all, GMAC claims to have spent so much money on each of their questions, so why not take it a few more times to make those questions worth while.

But jokes aside, what's important is that - GMAT will never ever in its life define who you are as a person, regardless of how many times you've taken it or whatever score you've got, nor will what MBA program you go to or how much money you make. At the end of the day, it's your perseverance, your diligence, your integrity, and things of that nature that really define you as a person.
Moreover, why putting so much pressure on yourself? Nobody has the power or right to put pressure on you other than yourself. Are you worrying too much about other people's expectations? Are you worried about that your parents, your friends, and your co-workers might look down on you if you don't get certain score within whatever time frame or number of tries? Do you feel like you have to get a certain score just because many of your peers or friends were able to achieve that score? If you experienced any of these, you are just putting too much pressure on yourself. And most likely your perceptions of other people's expectations weren't even true! Your family, friends and closed ones who truly care about you would never doubt or despise you no matter what score you get. Even if there were some people who would look down on you, why do those people's opinions even matter? If they want to laugh at you, let them be! Because they have every right to do so! Weren't you even laughing at yourself and thinking how pathetic you are after so many fails? If you can laugh at yourself, then why can't they? You need to relax and let your guard down a bit, you don't always have to be so tough, you don't always have to be so perfect, you have every right to be vulnerable, just open up and talk to your family and loved ones. Let them know how you feel, show them your soft side, let them know how much of a struggle this GMAT thing has been for you. I'm sure not only will they not laugh at you, but instead they will support you and encourage you even more. The point being, it's not about how you fall, it's about how you get back up. And don't be so stressed out on test day, try treating each real GMAT exam just as a practice test and just enjoy the whole experience. See it as a learning opportunity or a little assessment for your preparation work rather than a test. Each single question can offer so much to learn, regardless it's grammar, logic, or just general knowledge, all of which will make you more knowledgeable and skillful. And as someone who has taken GMAT several times both online and at test centers, I would always recommend you to take it at test centers. As there are just too many factors that you can't control in online exams. Other than tech glitches you mentioned, I've also experienced proctor issues, log-in issues, test environment issues, outside issues and etc. All of those things could go wrong on test day and affect your mood and ability in the exam. On top of that, you already paid a good amount of money to take the exam, so why not go there and experience the facility and service it has to provide for you? Let the staffs at the test center do their job and serve you, that's what they are paid for right? Lastly, 700 is already a pretty good score. As a last resort you can still apply using just this score. If you excel in other areas in you application, which I sense might be the case for you, I'm sure your GMAT score won't be a deal breaker, and you probably still stand a very good chance against others with higher GMAT scores.
Normally I only come to this forum for question explanations, but somehow I stumbled over your post. So this may be destined. Not only it's an opportunity for me to possibly help you, but it also allows me to open up and share what I have been through. After writing all this, I realized that I was talking all over the place. I hope this isn't too hard to read (as I really suck at writing), and it can offer some help to you and others who need it. Good luck in your GMAT journey, don't put too much pressure on yourself and as long as you don't give up, you will get there eventually!