yer I agree I'd block him and if he notices you've gone just say you left as you'd had enough of it. He will not even see your name on other status with mutual friends so he may well think you did leave
As sad as this is to admit.. facebook it the nearest thing I have to a social life, and he knows it, so if I told him I'd deleted my account he wouldn't believe me anyhoo!!
aren't your kids on FB anyhow? if so why does he not just add them if he wants to keep an eye on them
Also if you go into the privacy settings for your account you can block him from seeing individual things only. so you could block him from seeing your statuses but he would still be able to see your photos etc. That way he will not think he is blocked and will just think you've not posted any statuses.
One more question.... If I reply to a friends post, who's not on my ex's friends list, can he (the ex) see what I've put..? Or should I play safe and just chat through IM's..? Been bloody deleting all afternoon.. got all sad when I came across the statuses around mum.. I'm going to light her candle tonight - 26 weeks on Sunday...