The SAR for Nexus 5X is very hard to find on the web.
Go to http://www.lg.com/global/support/sar/sar. In the boxes at the bottom of the page, — Select Category — Mobile Phone, then search on LG-H790.
Results I get are:
-Europe & Middle East & Africa & Asia & Oceania
The highest SAR value for use at the ear is 0.607 W/kg (10 g) and when worn on the body is 0.397 W/kg (10 g) at 15mm
-USA & Canada
The highest SAR value for use at the ear is 1.25 W/kg (1 g) and when worn on the body is 1.28 W/kg (1 g) at 10mm
The FCC Grantee Code is ZNF, Product Code H790. Search here for much too much to sift through: https://www.fcc.gov/general/fcc-id-search-page