Hi there,
Thanks for your post. So your profile sounds like it has quite a mixture of strengths and weaknesses, to be honest, as it sounds like you know. On one hand you could make the case that your work is interesting/less common and you could potentially build some interesting stories there, and it looks like you have been able to develop some leadership and management skills, not to mention demonstrate commitment and passion. The 750 GMAT is great. And you feel confident about things such as essays, recommendations, interview potentially. On the challenges side, certainly the undergrad situation is the largest looming issue, and at least you are showing determination in working towards that, and will explain in the optional essay as best as is possible. There's also a bit of a potential challenge in that executive assistant is not always thought of as a role that allows a lot of leadership and initiative opportunities.... from what you described in your career you have had some of that, so would certainly want to play that up, but it's another challenge.
I have occasionally seen some schools show some interest in people with a similar undergrad situation, though often they apply a bit later after completing the degree, and if successful, are rockstars professionally in terms of what they've accomplished. Even with the awesome GMAT, I'd feel like your best chances will be outside the top 25/30 or so, and you can look at things like acceptance rates to see what schools are higher and lower and apply to a range of choices potentially. Haas, from your list, has a VERY low acceptance rate and is probably going to be close to impossible, partly due to their smaller class size and larger # of apps. The others are also all quite tough; maybe pick 1? 2 max? Again confirming with them about the degree.... but look at others further down the rankings (as a rough rule of thumb), or give it a few more years and THEN apply.
Side note, you have not mentioned your post-MBA goals, keep in mind those can play into admission chances too, as you make a case for why you need this degree etc.
Best of luck to you on your decisions and congrats on working towards that degree!