Hi and welcome to GMAT Club!
Congrats on your awesome score! That's 99th percentile and basically the highest percentile anyone could get... You should feel good about the work you put into it. We are not measured or ranked very often and so many tests (including GMAT, frankly are so flawed) but it is awesome to get a 99th percentile in something, esp something as competitive as GMAT. You should give yourself a lot of credit! This covers your undergrad "C"s showing that you are not stupid but were just disinterested or perhaps not clicking or distracted.
You can get started by checking out the
WAMC tool and seeing what it suggests for you (it makes some general assumptions but you can fill out as much as you can to get a sense of your chances) but I feel you can aim and shoot higher than Georgetown. Worst case, you can a sizeable scholarship at Georgetown.
By the way the class of 2022 has already started this Sept (it is based on the graduation, not intake year), so my guess you are saying you are applying for the R1 2021? is that right?
My suggestion for selling yourself would be to work with someone who has done this - current student or an alum. I am not sure your boss is a great candidate for this (they can definitely be a good sounding board and people love to give advice, so it is always a good idea to ask for advice) but in general I would suggest leveraging someone you know who has done an MBA. If you don't know anyone, you can hire an admissions consultant. That's kind of the same thing but you are paying them to be your "friend". Another option is to brainstorm and go through the
ApplicantLab. It may be a decent idea to get it anyway even if you are working with someone or have a friend since it works well to organize your thoughts and splits the elephant into bite-size pieces, though the next year's applications are not read yet, obviously. Anyway, it is $350 but not a must have. Many have applied by networking with current students and alums.
As to your story, the key is to demonstrate initiative and resourcefulness. Everyone has different resources. Some have gone to a private prep shcool, Stanford, and got a job at Goldman Sachs but that does not mean they worked hard or overcame adversity. What you want to show is that you have done more with the resources you had than others in your position. You could have gone to a small school (a bit of a weak point) but have managed all these other things at work or on the side. Sometimes you get stuck in your job/career because of your boss or you work for an org that has no room to grow but did you just give up or did you keep trying?
There are many ways to show progress, initiative, and passion. These are important for the admission process. Schools love people with a plan/vision/goals who are working towards something they believe. The overall "selling" process is not just 3 bullet points but rather a cohesive story that goes through your essays, short answers, LOR's possibly and definitely your resume. Resume has become super important in the admissions process so don't ignore it and make sure you create the MBA version (lots of videos about it on our YouTube channel - it is diff from the job resume).
P.S. It is good you are planning way ahead - that's awesome. Starting now will allow you to do some corrections possibly options to fix some of the blemishes or deficiencies in your profile.