Brenflor,
If he wants to marry you, he may not have a fetish that he will satisfy with anyone else or even alone. He said it would feel bad to satisfy it with you, didn’t he? I’m of the same opinion. I believe there’s no place for masturbation in marital life - even if some theologians go out of their way to justify it if it’s “in the context” of a full marital act. I believe it’s a disease and diseases need to be cured, not harboured.
As for cheating, you can forgive everything, but you can’t really put up with it on a constant basis. Or can you? If you were married, maybe. Seventy seven times… But forgiveness is tied with regret and wish to repent. You can’t really be with someone who does horrible things to you without even realising or without controlling himself enough.
As for prenupt, sorry, you can’t marry under a future condition, i.e. that it will only have been marriage if he doesn’t cheat on you until you die. Normally, you aren’t obliged to continue marital relations with someone who’s cheated on you, but that’s not a reason for divorce. In most cases, prenupts make marriage invalid. In your case, it would be possible that he weren’t intending exactly what the Church understands as marriage, that he’d be making allowances for other things, and that you wouldn’t be giving herself totally to him, but rather making reservations - if he doesn’t do this or that. If I were the priest to bless that marriage, I’d freak out. You certainly need to work all the issues out before you marry.
Already at this point I could enumerate enough potentially nullity grounds to make a canon lawyer shake his head (I’m a civil lawyer with a bit of canon law course and study under my belt). Potentially we have exclusion of fidelity, exclusion of indissolubility, a future condition, lack of sufficient use of will, lack of sufficient understanding of marriage… Let me just add that marriages of doubtful validity are not to be celebrated according to canon law.
All in all, MCGar is right about the vacation. If you want to keep him, he needs to work it all out. At this point, because of all the abuse you’ve been exposed to, you might have developed your own issues - not sure if you need to see a therapist about them, but it won’t hurt. You certainly could use some external help in setting your emotional life straight after all this.
And you have my sympathies. I have had one relationship that broke apart because of not only the bad things between us, but also masturbation and other troubling things on her part. It had to break apart and I wasn’t quite able to do it. Thankfully she came up with her own reason to break up. Some time after that, I ended up in a relationship in which unchaste things didn’t happen (well, at least not overt ones), but exclusion of progeny popped up (i.e. she didn’t know if she’d ever want to have children), as well as some other things. That relationship, too, had to go. Again she did it. But sometimes one needs to end one himself. You did just that. In my opinion you did right. You don’t need to get into a relationship with another guy now and you can also wait and see what turns out with this one. But you don’t really need to be his girlfriend until it’s clear.
And once again you did a good thing calling off the wedding. You need a real marriage, not one in which you don’t even know the person has a sufficient use of will, let alone what he intends by the oath.
Because if a man can date for 2 or 3 years without sex, you’ll have a pretty good idea he’ll be able to go for sex and be faithful to one woman once he’s married.