I haven't met any Taiwanese for the last two weeks, since I've been a little busy with exams. Seems like the Taiwanese I mentioned earlier use /g/ sound more often than I thought. So 二 is gi7 and.. well, another word I can't remember right now.
And guess what, I've just got to my parents 2 hours ago and I had another Taiwanese textbook awaiting me (Okay, it might sound stupid, but I'm collecting Taiwanese textbooks now). Listening to the recordings, I was surprised to found out that besides l, d, g and j, seems like z is also possible in some words. At least of the speakers on the recordings clearly says a /z/ in 熱 (zoah8)... He pronounced it that way throughout the book. Need to check whether he does that with other words too.