As usual, a most enjoyable story from you. I like the mixture of good and bad effects on Harry; real life is generally messy that way. I rather suspect that Hermione will be communicating with Harry by more than just letters, given her new access to fast transportation.
I'll admit, I do rather hope that a cure for his condition can be found.
That was a most unique use of Snape and he did it to himself; no one forced him to take that action. I have to wonder how that draining effect through the mark affected other Death Eaters? 'Twould be amusing if Tom ended up signing their death warrants, too.
Author's response
I imagined it as affecting DEs exactly like Snape, although for a shorter time and to a slightly lesser degree. Suspected DEs were in custody, and were under observation. Those that did show the Mark would be questioned under truth potions -- no 'imperious defense' allowed!