A bit of help regarding to numbers/times

I'm learning Japanese from Genki booklets, and I might've missed an information on how to write/understand Japanese numbers. So, please correct me if I'm wrong. I rather be corrected by a mistake than making a fool of myself trying to communicate with Japanese with error on understanding the number.

So, I understand with fact "juu" means 10. If I put the "juu" in front of the number stated, it remains 10, but if placed after the number, it "is multiplied" by 10. Like: yonjuu means 40, right? I understand that clearly, but does number of kyaku (100) follow the same suit?

Such as: hyakurokujuuyon. If I understand correctly, it means 164.

Also... When someone askes me "ima nanji desu ka." And if I look at the watch, it says 8:30 AM. How do I insert the A.M. in the sentence?

Is it "gozen hachiji han desu" or "hachiji han gozen desu"?

Thanks for your help!
P.S.- Sorry I had to type in romanji, because this computer doesn't have Japanese IME enabled at the moment.

You'd use 'gozen hachiji han desu'. The am/pm part comes at the start. And you've got the rest of the numbers right too. Good work.

arigatou gozaimasu!