How do I draw boundires?

I was reunited with my BF 9 months ago. (I had hired an intermediary. birthmom wanted no contact & told my intermediary she regretted not having an abortion due to my request for contact!! Ouch) Although things were very negative with my birthmom, my BF & all of his family have welcomed me with open arms. It's nothing that I would've hoped for... like a storybook ending. They are genuinely good people that have a very large and close extended family. When we first met we talked for hours... too much probably. He was very patient with answering my questions over & over. He's a wonderful guy& wants to be my father. I was very close to my AD who died 5yrs ago & I have no interest in replacing him. One of my biggest regrets was that he asked me to call him Dad & after many tears I agreed hoping I would feel ok about it one day. It makes me sick that I didn't have to courage to say no. He said it set the tone for our relationship & that he didn't really want to talk with me the same way he does with his sister, but like a parent/child. Now I feel there is no way out of it without seriously damaging the relationship. I hate it, I hate it. My AD would be brokenhearted if he were here. I could kick myself! I now call him Dad to his face & by his first name to my family. :( I feel guilty, but I find myself avoiding him. I don't want to give him so much time. I'm 40 yrs old & raising two teenagers, after all. Thankfully we live in different states. I don't want his parenting advice or lectures about watching my cholesterol & sodium... or about how my husband needs to quit smoking. Now we are reduced to talking about the weather & the condition of his stupid yard! (His project since he retired) I feel like he wants too much from me, but since I didn't draw any healthy boundaries at the get go, I feel like he thinks I'm rejecting him if there is the slightest hint of me not being available to email or call. Then there is a weird vibe. Also, he lost one of his kids to suicide about 10yrs ago, so I think he's especially sensitive to the feelings of losing me. I don't think I can talk to him about this. He would be very hurt. Sometimes I want the relationship & sometimes I don't. I feel like a bad person to think these things..... they've been so good to me. Is this that "push/pull" thing I've heard about? Do I have to keep faking things? I feel like I have to perform on the phone.... be more enthusiastic & interested, you know. Is it just best for everyone if I keep it up? Am I obligated because I'm the one who initiated contact? What do you think my obligations are in this relationship?? If I was going to say something, what could I say that wouldn't hurt him? Urgh. I'm in a pickle. Please tell me what you think... I'm completely open. Thanks