Dealing With Difficult People

 I think her anger is reasonable given the history, but at the same time, she should be supporting her son and tolerating you for his sake.  She may be doing so already, I don't know, so perhaps (in light of the history here) having you with her and your dying FIL is too much for her to bear.  Keep in mind this is a very traumatic time for her.  In other words, she isn't out of line to feel this way about you IMO, but she should've kept it to herself.

I think you've done all you can in terms of extending an olive branch to her.  The only thing I think you can do at this point is to concentrate on your M and hopefully get some MC and IC as well.  It is up to your DH to speak to your MIL regarding his expectations of her WRT supporting you both, and he is the one who needs to speak to his mother about her hostility toward you.  Stay away and don't push yourself on her. 

When your FIL passes away, stay in the periphery of your MIL if you can.  I would strongly suggest that your DH talk to your MIL before the funeral occurs about any scenes she might make or open hostilities she may make known.  It is not the right time, and I think she would tolerate you for your DH.  DH should be the intermediary, since he made known your transgressions to the one person who would hold a grudge against you far longer, and far deeper, than anyone else.  It's up to him to smooth it over as best he can.