Step Families Support Group
Traditionally, a stepfamily is the family one acquires when a parent enters a new marriage, whether the parent was widowed or divorced. This community is focused on many of the relationships and issues that may arise within stepfamilies where you may find answers from some members and you may help other members with their questions.
My advice to you is this. Yes, you need some private time with your soon to be boyfriend.
Kids at 10/11 going into teens start to become aware of this. My son went from having the bathroom door open, to ALWAYS having it shut and wearing a robe in the span of a few months...all around age 11-12. If I was in your situation right now, I'd look for having a certain number of hours with the door shut and/ or locked. Not all the time, but a few hours.
His dad should have some talks with him about change. About all changes coming with both good and bad. Go from being a little kid, then you get more responsibility, but you also don't get Santa. Fewer numbers of toys, but you get a few more expensive toys. Middle school has better lunches...but more homework.
And dad getting married would mean sharing him more, but also having more family...
He also needs to know that all feelings are okay (love, hate, anger), but all expressions of feelings aren't okay. There are things that you can't say (or shouldn't say) EVER, things that he can only say to his dad in private.
As far as kids manipulating their parents...that's healthy. As far as parents being manipulated by their kids...that's Not. In other words, it's not the kid's fault if he pleads for candy and dad gives in. The kid is doing what they're supposed to be doing...the dad is not. Parents draw the line and establish what behavior is acceptable.
And if dad can't do that...then dad's got major issues.