It seems that a site that explains the stats themselves can be found here. It'll just allow people to see full details on them.
How much rating (e.g. crit rating/penetration rating) is needed for 1% of the stat?
As far as I could tell via forum entries and blog posts the answer varies. But there is a forum post right here that says
Amount of Rating needed to reduce damage by 1% is between 23 and 35 in this sample.
This seems to be the same throughout all stats.
I thought that this may be of some assistance when it comes to damage. Lower down it explains what can increase your damage. The entire thread is all about healing and balancing that with attacks. It also explains how to glyph (which is handy).
Is there a cap on certain stats? (e.g. crit)?
Lyrion said that the cap for critical/penetration and hit was 440. This is false. This forum shows users who have experimented and have found that there is actually no cap.
How is combat power exactly calculated out of my stats?
Unfortunately there is no finite answer in this. After searching on this topic for about an hour. This is what I have concluded: Your stats are extremely loosely related to the 23-35 points above.
How much hit rating is required? (cap for pve/pvp?)
This is your last question. However it was tricky to answer. The forums are vague with this, always seeming to answer it but actually switching to a new question. But in here scroll down to look at sorrah's answer. I think it'll somewhat explain the hit rating requirements.
All in all your question can still be expanded upon. Since this exceeds the limit of characters possible in a comment I made it an answer. Hope this helps.