that would require exponential effort as opposed to targeting the person of interest. If they are willing to expend that effort they would probably seize my server.

wrt to the 5th that was my original point. If someone else controls my e-mail the fifth does not apply as there can be no self-incrimination by a third party.

wrt e-mails being sent to me, that doesn't really matter unless the party is replying to something. Even then e-mail headers can be forged. To really make a case a prosecutor needs to nail down that the contents of what is being replied to originated from me. Hard to do w/o my server.