Oh man, reading this sent chills down my neck. Our stories are very similar OP.
Back in 1999 my father had a major stroke at my family summer home on Vancouver Island, BC. I was 11 at the time and really had no idea how my life was going to change.
According to my mother my father was a monster, someone who lied and abused her constantly. She would tell me stories about how he left her in the rain to walk home, or how her mother had to send her a cheque so she could buy groceries for us (I have two older siblings, brother and sister). Long story short she was always shit talking him. I heard it all the time, I still hear it.... looking back it was mostly just a tactic my mother used to ease the process of attaining custody in court. My mother took full custody because my father was brain injured from his stroke, but I digress
What did I learn?
Well, fast forward through years of child therapy. I learned that if a child states that a parent or guardian hit them or abused them its taken VERY seriously. Just like you, my lie-filled, distraught, confused 13 year old mind thought it would be a good idea to say my dad hit me.
Cause hey, I'm the one that needed attention right? Wrong.
My mother remarried and in similar fashion to your case, my step-father and I never formed a close relationship. Specifically due to the fact that my mother and biological fathers divorce was so long and messy (10 years, close to 250k in legal fees). My step father claims to have lost over half a million dollars due to my mother, and honestly I don't doubt it.
MY DAD: My real dad.... Man! What a guy, he has had four strokes, and oesophagus cancer. He's the true definition of a survivor. Back in 1999 I found him on his bedroom floor nearly dead, not moving or talking. Quick work from neighbours and the STARS helicopter team saved his life. After all that he still runs everyday, enjoys playing squash, hunting and fishing. He regained his ability to read and write, he learned how to drive again (cars and boats). He was a successful accountant before having his stroke, he even had his own practice. The guy was the coolest dad around, and always tried so hard to be a father in our lives.
My dad wasn't a good husband, but he was an amazing dad
He had his kids ripped away from him, my mom wouldn't let him see us (because of fear he might hit us). I felt so bad for him for so many years because he always tried to see us, he would constantly show up at my school just to say hi. Or he would call me and leave me these voicemails I couldn't understand (he suffers from aphasia which is a speech impediment)
My dad has unconditional love for my siblings and I, even after everything thats happened he still gets up and tries to be a part of our lives everyday. When I turned 18 there were no longer custody rules in place, therefore if I wanted a relationship with my father I had to build it myself.
Its now 2015 and I honestly love my dad, I'm a busy guy but we try our best to meet up at least once a week. Sometimes I don't see him for months cause I get called out of town, which I don't like. Heres why: most stoke survivors don't live more than 10 years after a major stroke, let alone having 4 stokes like my dad. He's very lucky to still be alive, and I cherish everyday I get to spend with him. He's my good friend, mentor, and father. No one can teach you how to be a good man like a father can. Thats why I think its really important you give your dad a chance OP.
You can go through life feeling enriched with the knowledge that you and your father have a good relationship, knowing that a little part of him and his life will live on in you. Or you can go through life wondering what could have been.