I went with the white Stamoid that GW used originally from A&J Canvas when I redid mine. On my 282 I had the blue Sunbrella.. I think both Sunbrella and Stamoid are a solid choice.. Have to say that the waxy Stamoid has been great with weather and stains so would get a tad higher rating.
I was able to get all the backside material out and get to the backside of the glass. I went with Coosa board and glassed it in. It really came out nice and has stood up over the last 5 years. I'd recommend it.
I always take them down and lay them flat or over the back side of a sectional in a spare room for winter with temp at approx 55 deg. About this time, I'll clean and polish the glass and put them up before splashing for the season. I think they last longer this way.
you certainly can take a shot at the fill lines and likely should. you'll be changing them if you do the tanks. this being said, you are at the time where the tanks likely need replacement.
Here is an example of a cam latch. I'd spend sometime poking around on the net. GW used a lot of Southco items in the past - still do. You may not find the same one, but should be able to find something that works. https://www.silver.com.tw/upload_files/a-lock-accessories/A050.jpg
Here are your hinges....
Southco E6-10-301-20 Series Adjustable Torque Position Control Hinge with Holes, Acetal Copolymer, 1.69" Leaf Height, 6.99 in-lbf Symmetric Torque, Black, Pack of 1