OKAY SO, I've been on a thread, (I don't know how to put links but go here
Aperture ring with manual lens on K-30 - PentaxForums.com) and the people here are having the same issues than me, BUT me I can't use the M mode since my mode-selector dial is broken, and only gives me access to P, TAv and AUTO/SCN so... yeah
The people also says that It's a well known default, and there's a petition somewhere on the net about it. HOWEVER, since I do not use my 50 1.8 and my 16-55 3.5-5.6 II WR, I was considering just to break the little pin that controls the aperture, so like that, no problem. But that's kinda... destructive, and even if my camera isn't under warrantee anymore, I don't really feel like doing that... tell me your thoughts, guys.