You have a lot to deal with. You may be transferring some of your other issues into the anxiety regarding the cardio issue. Easy to do and totally normal. Having the courage to leave a toxic relationship was a good step. Try to have a positive attitude that you can now make other changes that will improve your life and you may find things falling in line and you'll be in a better place. You can't underestimate the effect of taking care of your mental health when it comes to your physical well being. Having good support is important.

Good luck and try to not obsess over your numbers. I think you'll be just fine.