ん is versatile as a contraction, but when you see it in front of a d-row copula (like だ or で), it’s likely a contracted explanatory の (as opposed to possessive の), which doesn’t translate well to English, but the way I like to think of it is that it means the speaker is explaining or perhaps rationalizing something, so it’s there to soften the blow. Thing is, it’s thrown out so liberally it’s more of a “feel” to the statement than a literal meaning. The second most likely case is a rather lazy negation (most commonly 知らない → 知らん), and usually the mizenkei verb form is enough to go on. Usually.
て form is very common. ている (often casually contracted to てる) is indeed like a tense (active present), and for some verbs (most notably 知る) simple present tense is not present enough. There are other helper verbs used with て form (〜て-おく, to do beforehand, is a particularly nifty one), but without checking actual stats usually I see て form in the middle of a sentence, where it functions as the end of basically a complete sentence without fully closing it off (so, like one of several verbal semicolons in the language, but really an “and” most of the time). って outside this context, however, tends to be a form of と, and that’s a whole different kettle of fish.
The ゃ can be a contracted particle は (e.g. といったらありはしない → といったらありゃしない), but unless there’s some context I’m not aware of, ありゃ! on its own is an interjection, either of surprise (like あら, あれ) or of exertion (e.g. a kiai).
そう is also versatile, and I don’t think I could cover it properly myself. It generally does mean “seems” in that usage but sometimes it may not be the most pertinent “seems like” on the menu (especially if what you really mean is that there is a resemblance). The same usage also means “I heard that, rumor has it, apparently”.
So, IMHO, that’s the 80/20 version of what’s going on with those, to keep a once-every-few-years post as short as I can manage. Probably someone has a legitimate disagreement.