Following Local Machine's advice, I re-torqued the bolts over the weekend and it helped a lot. They were seriously loose, and I don't know why. If they get loose again I am locktite-ing the crap out of them. (also replacing gaskets for peace-of mind)
The oil was milky as fuck and I wish I was blind not to see my brand new piston bathing in it.
But I know this happened within a week because the oil I drained last week was perfectly healthy.
As for the ebay gaskets, I already have a set like that. Be careful about those, guys, the head gasket that came with my 'set' is a 2 mm thick piece of shit that is made of 3 layers (cork-metal-cork). I am sure it would cause more trouble than its worth if I would ever put it in the engine. I would expect reduced compression and near-impossible removal compared to the original metal gasket. So that's what you get with a 40$ kit. You have been warned.
About servicehonda, they used to be reasonable. I did get my piston and rings and several other pieces from them with reasonable shipping. I usually order from wemoto.com in UK, they deduce tax for international orders and offer very reasonable shipping. But in this case the gaskets are non-stock and would take several weeks for them to acquire (I know from experience).
So I fixed the bike and changed the oil on Saturday and went for a ride in the woods. My starter engine died the moment I got out of the woods. Turns out I've worn through a set of brushes last week while cranking the shit out of her.
Little bastard sure is getting expensive to maintain. :)