Second and Third Questions
The center post table is a friction fit, so no adjustment to make it less wobbly... This design is inherently wobbly, but it's less of an issue when using it.... Options to make it less wobbly would be to add a second floor cleat and a second pole... One of the A-frame owners here also added a hinged stabilizing plate to the camper wall, that connects the end of the table to the wall and does a good job of stabilizing.
I took out my heavy folding leg dinette table and replaced with a single pole assembly and then made a new tabletop that is more square than rectangle, wobbling is not an issue. The table bridges between the two dinette seats when traveling so storing it is not an issue and it doesn't move around.