Installing https plugin solved it. there were 2 separate problems:
1) infinite loop
2) assets being served from http
The plugin solved both, the first problem solved by adding .htaccess to the root (which I tried milion times, but apparently I must have made some mistake in the rewrite rules).
But that doesn’t solve the issue with assets (I know, I tried/tested). That means this pugin has to do some magic in php as well, which by my logic is a pretty big issue in the wordpress itself…