Chain and gearing

I have a converted wr250r to x and need help with a chain and new gearing.

The bike came with 12t and 45t, but I feel it's to aggressive for me. Also a few months back the chain clip came off while I was riding and the chain dug slightly into the case next to the front gear.

So I want to replace both front and back gears with a new chain with something a little less aggressive. Also taking into consideration I'm gonna lower the bike with the stock shock.

So what size should I go with? also what chain and how many links?

Thanks

Just go with a 14 in the front and 42 - 44 in back.
The r came with stock with 13/43 gearing.
O ring should be fine, but you could upgrade to an X.
Length no idea, but a stock chain most like will need to be shortened.