I'm really sorry for the loss of your mom and the relationship.

I think it is inevitable that anyone is going to struggle and hurt when they are dealing with the things you are currently dealing with. The death of a parent can be really hard, as well as the end of a relationship, are two of life's biggest challenges for anyone. So to me, it makes total sense that you feel a bit unstable/lost. Grieving is not easy at all.
On a practical level, just being aware of those emotions and validating them is a big thing. It's easy to get lost in the emotional maelstrom when all these things are going on. Remind yourself, as many times as you need, that it's OK to grieve and you're not always going to be or feel perfect. Sometimes things just need to process and it's like watching a kettle, I find. We think and think about the things that are hurting us, feeling like we aren't making progress. but in those moments where we are least expecting to find closure and peace, it stumbles upon us as we are just living our life. And there comes a time when you realize the memories don't hurt so much, you filter out the pain more and more and you find happiness and contentment in the memories of loved ones.
As for the pull between opting out and continuing - I really like to think of those two things as being like two "parts" of me. Two pieces that I haven't been able to reconcile and allow to make peace with each other, and that's OK. There's the part that knows how much life can hurt and wants to protect me by opting out and not allowing any more pain in. There's the part that also knows there's so much happiness, beauty, love, etc to be had, and wants to keep going and making things better. I recognize the hurting part, the part that wants to quit, as sort of a hurt child who just really wants safety and for everything to be the same, to be blind to the bad things that happen in our lives. Those feelings are all coming from a place of hurt and it's up to "happier" me, "stronger" me, to always remind the little one about the good things and that everything will probably be OK if we just stick in there. Those parts of me may never be in full agreement, and that's OK.