While not an answer, this is the only way I can post a picture.
Here is what a properly installed lintel looks like, at least in my mind. Note that the bricks overhang the lintel by a tiny (1/4"?) bit.
I think your choice of 5/16" size lag screws, 2-1/2" long, is fine. I would say 3/8" is overkill but if you just like the look of the bigger fastener, it would be fine.
I'd actually use something a little smaller, but longer - 1/4" size, and 3" long. (And washers, whatever size you use, I'd use washers.) One of those is adequate to ...
Are you sure your steel beam is a W16X26?
I doubt that beam needs lateral bracing, because that size beam will support about 31,000 lbs. per foot for a 20’ span. (That size beam can support my entire house and 3 of my neighbor’s houses.)
Lateral bracing is required when a beam is fully stressed (or overly stressed) and you need to keep the beam from buckling ...
Would it be legal, on the west coast it would be.
I would reconsider and at least get a paint on wood preservative and put a coat on it prior to building the deck. Moisture is not the only issue with wood outside.
I live in Oregon and have lived in California and Washington state. I have built many decks and replaced quite a few. Some of the issues with ...