I have to agree with what everyone else has said, especially Fenstar... Sorry, but it's just the blunt truth. It's baffling why you would come looking for advice from a forum of highly dedicated, and in most cases highly experienced Bengal owners, yet not ever want to follow any of the advice that's given... Are we supposed to use 'reverse psychology' and tell you to do all the wrong things assuming you'll just do the opposite?
Personally I would do what others have said, and try to reintroduce them properly, giving them time. Also I would continue to use the Feliway - as long as it's not creating any negative effects that you can tell, it could be helping, even if only a little. I have used it in the past for similar issues and it seemed to improve everyone's mood to a degree so I do think it's worth it. It might also help if you can do something about the cat(s) lingering in your yard, as that may also just be adding on to their stress.
It will take work and dedication on your part to help things move along smoothly. If you're not willing to put in the effort and really help your cats live happily, it may just be best to rehome... And I only say that because in that case, that's what would be best for the cats. Imo it wouldn't be fair to force them to live together unhappily and always stressed/fighting if you can't figure out a way to solve the problem.