I used NiceMod for new building block, but somehow it screwed pathfind of villagers, will this mod solve the pathfinding problem since it says it will implement "Multithreading for AI nav pathfinder" on the upcoming update?

Unlikely, most changes we target are for performance improvements of the game. Since this may be modded interaction it is even less likely. As it is possible the mod NiceMod did something funky with their block collisions.

But, could you please take a look and give a little hand?

Didn't take me a minute to find. Here is the problem, this method needs to be properly overriden to return false, or completely removed, for all the blocks where pathfinding breaks. https://github.com/MIUNO/NiceMod/blob/46f3ac28070163cc7b04727c06305897a4d3b393/src/main/java/ru/miuno/nicemod/blocks/block_types/HorizontalHalf.java#L99-L102

THANK YOUUU