3 is like a hard "A" as in the word 3youn - eyes in arabic
the 2 is also used as an apostrophe when put in english font like ba'a and it's kind of as a pause I'd say an "uh" sound
Other numbers used:
the 5 - is like a KH also I've seen some people put 7' so it looks like the letter itself with the dot on top.. as in the word dakhlak.. it would be da5lak.. or da7'lak.. meaning please
8 - a Q sound as in Qur'an or qasr being 8asr - meaning castle
6 - a T sound as in e6alla3 - etallaa - meaning look
and as you mentioned the 7 being the hard H sound..
anywho those are all the numbers I know of and have seen

hope that helped a bit