Give it a go. I couldn't get focus on nearby objects. I could have put the scope in the car and used something at a distance. I chose to wait until it was dark and then set up the finder scope. I reckon your focus adjustment will be enough.
Chances are it will be about the same place as one of the eyepiece focal lengths when you try the webcam/N0 11 keychain camera. I had seen a comment somwhere else from a guy who found the webcam needed to be way inside the normal focus tube distance.... I can only assume he was doing something odd !
I wouldn't bother about an IR filter. As savage 40 said the webcam/keychain camera is not going to be good for objects like start clusters and nebulae.
It will be most use on the moon and planets. The moon isn't a problem
I haven't tried Jupiter yet as I have been building a new dobsonian mount.
I splashed out on a sheet of plywood to build a new mount for the telescope I built approx. 30 years ago. The 8.5 inch scope has not been used for a long time. A new surge of interest, more time to do what I want and the old, somewhat wobbly, mount just had to be replaced. It's virtually finished and I reckon Monday night has good clear conditions forecast.