You have been - and remain being, it seems - far too casual about planning and executing your career.

Getting a good GPA and double majoring with comparative literature will not *per se* open a range of alluring career vistas for you. You have to hustle for the next step just like everyone else.  No one wants a casual Dan working in the organization. While your past university may be top 20 in US, it may not be anywhere near top 20 in math - that is a different thing entirely.

Even at this stage it might be helpful to you if you were to seek feedback from the top math graduate schools that rejected you. My impression is that your curriculum may have been more limited than you appreciate. The second major that you chose might also be a factor indicating a more limited focus. it is important that you make clear in applications that your focus is now on math and literature will just be a pastime for you.

Another thing you should do is engage with your undergraduate university's careers office to see what possibilities may be there for you. If you enjoy friendly relations with any of the professors of math at your old department, you might seek some advice off them too.

I think that your rejection of an acceptance at Bonn was foolish: the more so on the specious grounds that you offer for rejecting it. Please do not ever reject another offer of a place without consulting some competent academic on the matter.

Ideally, if you want to do postgraduate studies in France, it would be best to go and work in some capacity near Paris so you get up to speed with the very fast speech of Parisiennes prior to starting the MS.

But failing that try to get an internship/research assistantship that encourages you to pursue any missing math courses during the evenings over the gap year. Look through academic job listings, send out CVs to government research bureaux, job agencies, newspapers, etc.

Hup to it.