Deck/Dock Rebuild advice

All thanks in advance on this one! I had a couple of rotten boards on my deck and when I pulled them back I found multiple rotten joists as well. Discovered that the rotten part was an add on to an original boat house and likely done on the super cheap by a sub par contractor judging by the fact that above ground rated wood was used for critical and not critical components.

Some things that I need some help with:
it looks like the beams are merely lag screwed into the pilings. I don't think this is correct and should have been notched and lag screwed or carriage bolted. What can I do about this?

The lag screws look a little rusty...how long should I expect a galvanized lag screw to last?

The ledger is 2 2X8 stacked on its edge? this doesn't seem like the most sound way to support the joists?

for the triangle "wings" on the rectangular deck I changed from a single 2X8 beam to a double 2X8 beam attached with 3 structural screws on each contact with the main deck frame vs 2 lag screws per end. the longest double beam is 10ft. there is no post or support at mid span. Basically all of the support from those beams are on the 2 connections to the main deck attached with structural screws. what are your thoughts on that. Perhaps adding a post mid span is a good idea?

is it common to not notch beams to posts? Even my wood deck by the pool uses 2 2x6 beams that are just nailed to the 4X4.

pics are attached.

Thanks,

Ryan