Anyone a clue when everything on the first level (small church including expansions) is built? My pomp for the clergy is stuck at 6.10 .

Seems you get a quest at some interval that lets you choose if you want to deliver some goods to the king or the church or the people. Depending on which one you choose you get kingdom/clergy/labor points as a reward.

As for the splendor, I got some from building the church but that is as far as I got.

Nope, the delivery doesnt' increase the splendor (?). But I found out, that my game had a glitch - once I built all expansions on the first level of the small church, everything else was greyed out. After leaving the game and coming back, I was able to build more of those expansions - which grew my splendor.