The achievement will be made generic so they're not specifically tied to Stranger Things and if you already have the current ones, they'll be automatically unlocked for you.
I've heard a few people with issues with Win 7 and the game, it's something I've brought up to the team but I must warn you that we do not officially support Win 7 and of course with it pretty much having reached end of life (only purchased security updates are being done), then more and more software is not going to work with it.
Actual farming is a very grey area...however it definitely crosses the line if someone in the party doesn't want to farm and they are actively being held in the game against their will and forced into it effectively - or you team up with the other survivors and kill that one survivor.
Simple solution - don't farm, a lot of players really dislike it and actively want to play the game properly.
If this is a recent thing that's started - can you explain exactly what you mean by lag please? Any video would be good as well if it shows what you mean.
You are free to make suggestions to Steam themselves in their forum for Steam related things, as this relates to them and not us. The game uses EAC and not VAC - if you want to suggest Steam how to treat VAC banned accounts differently, the Dead by Daylight forums not the right place.