Daffo I didn't actually just tell my ex to fuck off without trying to be amicible and trying to be civil before. After years of emotional abuse and him telling me what to do all the time and continuing to still try to control me almost 3 years after leaving, I reached the end of my rope. I over considered his feelings for WAAAY too long, and in return was not living the life I wanted.
He would openly admit he knows I would always do the best by the kids, which of course were my top priority when introducing my partner. Neither my kids, nor my ex knew about my current partner for a long time, until I worked out myself if the relationship was going anywhere and I understood my current partner etc. Despite knowing and acknowledging I would move at the pace I thought was appropriate, in his down moments he would still call/ text/email his conditions I "should" adhere too. My ex is a very difficult character who can flip between nice and nasty so quick you wouldn't believe.
Anyway, after telling him to fuck off and leave me alone, he actually did back off. I finally stood up to him after years of trying to show him how his behaviour was etc. Up until this point I was still receiving abuse at handover times and random calls/messages etc and it was affecting the kids.
I agree some caution should be applied to the OP, but sometimes abusive controlling men only speak one language. When he knew I was serious, he backed off. As OP is still living in the family home, if there was no prior abuse I think that some understanding of the ex shoud be taken into consideration, I agree with that. I had to draw a line as it was going on too long and I was continuing to midify my behaviour to pacify the ex.
It is only recently he has got the message he cannot control how I spend my money, what I do with the kids when they are with me (although I always inform and discuss with him anything important) and certainly not my future or current relationships. It has taken me a long long time to get to this point.