First of all, I'm glad you liked it
Hmm, the key, I should have placed it somewhere else indeed (stupid mistake), it's a master key, but it was never the intention that people whould stack up boxes to climb over the wall, there's absolutely nothing to do over there
The servant, I put him on absolute, so you're forced to be really quiet and not to wake him up. If you really want to blackjack him, it's possible while he's still sleeping
In the bedroom with the lady (minor spoiler):
just do a little floor searching