You are normal. You cannot expect to wipe away your feelings overnight. Of course you wonder these things, of course you wonder if maybe it will make the difference. Everyone has a hard time with break-ups and no contact and we all feel and think the same things. It is ok that you have mixed emotions, but you need to use your head when it comes to your actions. Your feelings will draw you down unhealthy paths if you allow them to rule you. You have to keep yourself in check.
A couple of quick thoughts.
1) He is not going to change. You dated him for 3 years, he is as old as he is and no kick in the a$$ is going to turn him into a different person. Yes, he needs therapy and no, it isn't your job to see to it.
2) Being the best thing for someone doesn't mean that they are the best thing for you.
3) How could he let you go? This is the key thing, huh. How can he just walk away, not care...did he ever love you? Why isn't he fighting to get you back? Doesn't he realize how much you did for him? This is what hurts. It is a self-esteem bruiser at the least. How can you care so much for someone and they find it so easy to just walk away? I don't have the answer...but I know that it happens. This is probably how my ex feels about me and many exes everywhere... No matter how much it hurts, you have to let this go because it will drive you crazy. What it has driven you to in the past is to work harder, give more, sacrifice yourself and tolerate abuse in hopes that he will realize how great you are. yes? The more he pushed you away the more desparate you became for him to love you? This is abuse and is not healthy. You have to let it go. Use your head to step in here or you will be headed down a self-esteem spiral. You know how this works in the textbooks, now you know how it feels when you are in the situation. Do not give into this, you have to fight your tendencies towards self-abuse. You are loveable, you are worthwhile and you don't need him to see these things for them to be true. You can live without his love and approval...and live better without them, in fact.
4) I really believe that he did love you in the ways that he could. Unhealthy people have limits on their feelings. You are feeling the negative effects of the limitations.
You are doing just fine. Your feelings are normal, valid and to be expected. Avoid the slippery slope and keep yourself mentally on track. I just know that you have great things ahead of you!