A little update...
Following the advices most people gave me here, I decided two weeks ago to pay a visit to my county's department of labour (Taipei in my case).
It turn out:
1 - Even though I'm on a 1 year, fixed term contract, since nothing is mentioned in the original contract, I'm not entitled to pay anything if I quit. NO PENALTY.
I'm only entitled to a 10 days prior notice (and the longer you've worked in the company, the more it grows).
If I had signed the second contract though, it might have been legally binding.
2 - The company CAN NOT fire me for any reason other than the ones mentioned in the Labour Standards Act. It cannot fire me for the sole reason that I'd refuse to sign another contract/agreement or new work rules.
I guess the error the company made, was to have me sign the first contract and process my work permit application, then only after that ask me to sign the second contract with all the shit in it. They probably didn't want to scare me off, or assumed that I'd sign it anyway and believe their lies.
Since my visit to City Hall, I discovered a lot more irregularities in the work rules (for which I had confirmation they are illegal) including some "fines" they are giving us. One of them is originally illegal, but they're very clever about it.
Whenever you arrive late at the office, the company deduct your salary by 1 hour fractions. So if you're late anywhere from 1 minute to 59 minutes, they'll deduct 1h. Now, it gets even better! They considered that when you're late, you're actually "absent from work without notice". Which means they count hours double (as a penalty)! So this morning, if you were late anywhere between 1 minutes and 59 minutes, the company will deduct 2 hours of your salary.
This is, according to the Dept. of Labor, absolutely illegal (they should charge 1 minute if you're late 1 minute; and no penalty). However, they systematically ask employees, as soon as they arrive, to fill the late arrival as 1h of unpaid leave. If you take a leave on that morning you were late, the company will cancel the penalty and only deduct 1 hour off.
This way, they turn an illegal penalty into something legal, by making it look like the employee took a leave. AND, they slowly take away your "unpaid leave credit".
Now, I've alway firmly refused to fill unpaid leave on late arrival because I didn't want to start eating away my unpaid leave credit (I should therefore be able to claim a few hours back). They tried to force me into it, claiming they would count the entire day as not worked, to witch I threaten to call the Dept of Labor. Turns out, it was in fact, just a misunderstanding (they're charging me 2h, but don't eat my unpaid leave credit).
However, I'm now pretty pissed and I've got one more question.
I've seen on the Dept of Labor's website there's a special unit named Taipei City Labor Inspection Office. Would I have any chance to trigger those guy's interest? Any thoughts about giving them a hint, and how?
Someone has to stop the b***s*** that's going on in this company and give those mofo a lesson. All my colleagues complain - and not only foreigners - but of course, no one take action.