The one danger in sharing your account is that someone else has control over it. If you don't know them well enough, I wouldn't think this is a very smart thing to do. If I were you, I would n't want to jeopardize my current income. You seem to making good money right now.
I have a site that makes 1.50 a click lowest click ever seen on it is 65cents- No I'm not going to tell the site or the niche so don't ask.. But I think you are worrying for nothing- If you pay dropped to .1 would you contact yahoo- No...so why contact them when it's jumped up...You guys are funny If yahoo wants to ban you they don't need your help.
How is shared YPN against TOS if me and a partner had a LLC company? Not that I do but if you registered with a company it should be perfectly ok. Even a limited partnership should work.