Hi Dexter. I think it is possible to have a good relationship with one parent and yes, it can be maintained but you and your father will both have to actively work on it and you both have to be committed to following through. It will require you both deciding to get together while accepting that your mother will get upset, she had proven that time and again.
Does anyone have any suggestions for me? I know my mother is sick, but she makes her own choice not to participate. I feel like my dad on the other hand misses out on so much so as not to rock the boat.
You are correct that your mother is making a choice here, but so is your father. Yes, she may make his life more difficult and yes, she probably uses manipulation that is hard to deal with, but he is an adult and gets to take responsibility for his choice to not rock the boat.
What are you hoping to have happen here? Are you looking for a way to be able to spend time with your dad and not have your mother get upset? Or is it something else?