S.B.
Dear M.,
It seems to me that you know he will pee or poop at a certain time at night so maybe he needs to be on the toilet before he goes to bed. Give him a nice bath, brush teeth and put him on the toilet. My dad made a stool for the kids to use to climb up and when they were little, I often used it to sit on to help balance them while they sat. They had potty chairs but didn't use them for anything other than stashing toys in.
If he pees or poops every night at a certain time, have him on the pot before you put his jammies and diaper on.
He knows how to get his diapers off by himself, so it might be time to let him wear training pants during the day and put him on the toilet every time you go. Everytime Dad goes. Everybody gets a turn at potty time.
My daughter got in the habit of pooping in the tub and one day, I just left her in there with it. I called my mom and nonchalantly talked about the weather, etc for about 10 minutes. My daughter started freaking out because it was the first time I didn't race in to get the poop away from her. And scour the tub and re-wash her. It sounds mean, I know, but she never did it again.
And, I put her on the toilet before her bath and after her bath.
You know he will pee or poop at a certain time so just tell him he can sit on the potty until he's done and then get into bed. You said it already takes an hour or more to finally get him into bed. Spend that hour putting him on and off the potty with no diaper until he goes. If that doesn't work, leave him in a poopy crib for about 15 minutes. Tell him it's bedtime and mommy and daddy are tired and they never poop their bed so you'll deal with it in the morning and close his door because you don't want to smell his "stinky".
Tearing his diapers off and pooping in his bed is NOT the routine you want to be in. 10 or 15 minutes is a long time for a kid to think you actually really won't clean up the mess.
I would definitely start him on the toilet.
I would get a timer that you can set so he knows that in one hour he needs to try to use the toilet, brush, etc and whatever time that doesn't take up, you can have story time.
It sounds to me like he doesn't really like diapers so it might definitely be time to potty train.
Peeing and pooping in the bed is a major no-no and if he insists....you need to try a different tactic. For sure.