Hi First Baby Eek!
Loopy lou dropped me a msg to see whether or not i could offer you any advice.
Well to start, the one email that was sent on to you is enough in itself to justify any form of action from you. With regards to the others, i'm going to guess that if you have access to his emails then they probably could be used but having said that I don't think you need them and probably not worth the risk as you have enough in the one email already.
Clearly his behavior is absolutely disgraceful, I actually cannot believe there are still employers out there that are stuck in the 1950's
having read through all of your posts its hard to advise what you can do as you have stated that you don't want to go down the tribunal route? to put it in basic terms you will win a sexual discrimination case (no upper limit on compensation!) hands down! It really is that black and white. i understand your reasons for not wanting to do this but it sounds as though the employment relationship has broken down so can you realistically go back there and work for such a nasty old fashioned arsehole?
So your other option is to go down the constructive dismissal route due to sexual discrimination and hope that your boss gets some advice quickly where he will be told that if you go to court it could cost him a significant sum as well as destroy not only his reputation but the reputation of his company. Id say 90% of the time he will offer to settle with you out of court (not guaranteed though!).
You mentioned about sitting down and talking to him but what are you hoping he will do? Offer to pay you an amount to resign? That is a tricky one because it may take away some credibility if he doesn't and you then want to take it further, or even go back to work after? You would still win a case if he did refuse but it does make it a little awkward if you have asked for a 'pay off'.
You literally cannot let him get away with it though, gosh it makes me so so so angry - its bloody 2012 and this sort of sexual discrimination still exists, terrible!