If you did not cheat then tell her to show you the proof. There cannot be any proof if you are telling the truth.
If he has given you a reason to suspect him of cheating, then absolutely. Assume that he isn't cheating until you have proof, though. Be careful of how you approach him with this: if he's not cheating then it might become an issue of him saying "you don't trust me!" or "why do you need to go through my stuff?". All in all, I guess just be tactful.
be as honest and sensitive as possible and make sure that you have proof that the person was cheating
Cheating is cheating no matter where it occurs and (with proof or uncontested) is still a legal cause for divorce. Abandonment is a different issue, particularly if your husband was in military service in Iraq. If the abandonment happened when he came back, that is another story.
I suspect that your Winchester may have been used in Canada...hence the British proof marks? I suspect that your Winchester may have been used in Canada...hence the British proof marks?
If he wants you to produce a phone bill, you should have nothing to worry about. If you aren't cheating on him it should all be fine. If you are cheating what is the point if you want to be with someone else divorce him, obviously he doesn't realize how good you are and wants to go for some other lowlife. If he is you deserve better, Get out there, Do your thing and hopefully it will all turn out okay.
suspect
no go straight to his house and murder him, chop his head off and watch him bleed out. Then fly to another country and start a new life there
If you have absolute proof that your husband is cheating with this other woman then you should deal with your own problems with your husband first and yes, the other woman's husband should know. This is not an uncommon problem and most people (whether a husband cheats with another man's wife or a wife cheats with one of her friend's husbands) is very common and the victim of the cheating generally does tell the husband or wife that their spouse is cheating with their spouse.
You either believe him or you dont, if you have proof dont.
get proof first...then just break it to her straight up
Pictures. Always. Or record a conversation regarding it. Written proof is always good.