Oh and his comments about sex are truly, truly disgusting. The kind of stuff a nasty bullying misogynist says. All vaguely dominating, crude, designed to objectify you. It speaks volumes about him as a person and it is no surprise at all how unhappy you are and how you can start to see how unhappy your children will be within this set up.
One solid piece of advice - I really do hope you separate, and a good tactic with a nasty fucker like this is to box clever over childcare. Yes, you are right, he would absolutely want to make your life as difficult as possible (you say this yourself, that this man you describe as an 'ok' guy would absolutely set out to make your life hell - tells you everything eh?). So yes, it would be 50-50, I want custody, messing you around with contact etc. Trying to hurt you and hurting them to get to you. All classic.
So - your 'position' is this:
'Well yes I hope you WOULD want 50-50! I've done all the work so far, I have no intention of letting you get away with just seeing them on a Saturday and leaving the parenting to me!'
'I'll be tired too. I'll need a break. It's your duty to do your bit with them, and that includes overnights.'
'We both deserve equal downtime and equal free time - I never had free time in this marriage because I always had the kids, that will change!'
and the KILLER -
'We will both want to move on and meet new people, we both need free evenings and weekend nights to be able to do that.'
A friend played this to blinding effect when her nasty shit of an ex decided he wanted to 'go for custody' of the kids he had barely engaged with since birth. She felt the same as you - they were her life. But she was clever. She knew full well he didn't want the time with them - couldn't imagine anything worse - he just wanted to fuck her over. So she started coming out with the kind of stuff above. Oh looooordy I've never seen such a rapid 180. Suddenly he was all about not 'being her babysitter on the weekend so that she can fuck other men' and not 'spending his time after work doing bloody homework with HER kids'.
Barely sees them now, she hardly hears a peep except the odd Saturday, he struts around thinking he 'won' - and she's absolutely delighted about it 