I don't think I would use a brush or any thing else that could potentially throw swarf up into the screw or bearings.
You could probably tape a smaller piece of hose to a shop vac and get that in there to clean it out. It will probably plug constantly and take a while, but that will still be a lot less time than having to pull the screw to clean it out.
For the stand, I think that would work well. There are advantages to having the machine level, so I would shim it back up. There a people who know better than me on that and I would wait for one of them to chime in.