She’s suspicious of you because she knows she’s doing things she shouldn’t, it’s total projection on her part and it’s not uncommon in a situation like this. You can still care for all of your kids and not put up with her bullshit. Don’t internalize her toxicity, don’t feed into her insecurities. You may not be able to do anything about separating right now and maybe that’s not even what you want, but you do need to take a step back from her and set boundaries with her. Whether that’s an in house separation, or keeping her at an emotional distance until you can get into some much needed couples therapy. The focus should be on the child who needs the both of you so much right now, the other stuff can wait.