Remember that because he is 2 months premature, that his development may be 2 months behind. 8 months is still appropriate for being fed by parents as well as not being interested in other self feeding activities. Unless he is showing other signs of motor or other delays, I wouldn't worry too much.
I would focus more on transitioning to a cup rather than having him accept the bottle on his own if he is rejecting this activity. Try the Nubby cups with the soft spout. You can also try little paper cups with water in them if you want to skip the sippy all together. As to self feeding, try things he can easily pick up like cheerios or the Gerber puffs.
If he's not by the books with his age adjusted for prematurity at his next check up, then ask the doctor for a referral for evaluation, or contact the special ed department at your local public schools for their early intervention services. They either come to your home for therapy services or you go to the school depending on where you live. My stepson was in early childhood special ed since before his third birthday because of developmental delays and he was 2 months premature as well. The prematurity was a factor in being able to secure services for him. It doesn't cost anything for the evaluation through the schools and if you disagree with their findings, you can appeal and have a private, independent evaluation done at the school's expense.