About your first suggestion, right now you can select several tags at once, but I think other options are either/or. Can't say how feasible it is to change that.
As for your second suggestion, a better rating system is in the planning stages, but for now all you can do is go to your account settings and make sure the checkbox labeled "Show content marked as adult in search & browse" is unticked. You can find it in the lower half of that form, under "Content". I'm afraid that's all-or-nothing, but it's there. Hope this helps!