Please add audio to this pronunciation. So far very little audio in this portion of the course..
It seems Duolingo doesn't automatically accept 's for is...we are trying our best to add this alternative, but as you can imagine, it'll take a while to fully add it considering how often you see this verb.
No, just plain "dirty". You'd need an intensifier to imply "filthy" - "fíorshalach" or "dubh salach".
And you wouldn't use "salach" for other meanings of "filthy" like "filthy rich".