1 - I never had that type of problem. Try it again with a wired mouse. Wireless mouse always have greater delay than wired mouse. It's because there may be interference between the mouse and the receiver.
2 - I also have error sometimes if I try to use WP into Darkwood. Level 2 Purgatory as always. Sometimes it gives error sometimes not. If you got error then rejoin and try again
Level 2 Purgatory as I know can't be fixed so deal with it
(Think like this is how it's intended to work, the part of the mod, even harder, you have the chance but will you surpass it?
)