And what about a non-Jewish woman for payment?

Assuming it’s permitted under the laws of the state, etc. etc.

First of all, it’s good that you’re asking and trying to overcome this, and of course it’s a legitimate question, but in my opinion I think it would be כדאי to consult someone who, besides understanding this and having both halakhic and general knowledge, also knows you and can give you advice that’s more suitable and specific.
And just as my own advice—maybe instead of going onto those sites, go onto matchmaking sites. Even if it were permitted, in my opinion it’s just a waste of time and it cheapens it.
In any case, lots of success.

In my opinion, no.

You’re struggling—try to learn and grow wiser: “Thoughts of sexual immorality intensify only in a heart empty of wisdom.”
Obviously that’s not a clear-cut solution, but it probably helps.

In the book Tanya it says that the sin of wasting seed is more severe than relations with a non-Jewish woman, but repentance for wasting seed is easier.

It’s easy to say “cope with it,” but even married people barely manage to get through two weeks, and I need to get through a bit more than two weeks [in any case, matchmaking isn’t a good idea, because even if I start dating now, it’ll take at least a year until marriage]