1- Should I bother with centralization higher than medium? I'm not quite sure how high my number of direct vassals may rise and that makes the vassal limit penalties sound quite scary.
2- How bad is it to be over demesne limit? I'm currently sitting on 12/6 titles and I'd really want to keep them until there are enough men of my dynasty to receive them.
3- Does opinion have any bearing on pregnancy chance? My new character is a damn cheater and his genius wife is not happy about it.
4- Regardless of the above, is there any way to get rid of the malus from adulterer/suspected adulterer or are they forever?
1) OOPs (edit : read Crown authority and answered appropriately...), sorry

New anser: tax your vassals (yes , also your feudal lords ) into space and don't worry qbout a small demesne, so.. keep more vassals...I don't have Conclave though...
2) Pretty. Reduces taxes pretty much, gives opinion maluses iwth vassals and all... as the tooltip should say. Depends.
3) No, not in general. As far as i know. Well, actually can, it's.......If they like each other enough (~75 i think) they have a really good
chance to fall in love and that increases the chance to pregnancy, but else..no.
4) No idea sorry.