on pics #2-3 I have used any type silicon... I used clear like they used on the factory bunk seam corner, you probably just need a small amount there
on pic #4 you may find that by wetting the seam threads they will swell and the drip will stop by itself... (this is called seasoning)... otherwise some soft wax rubbed on the threads will seal the thread holes
last pic... I don't think you need to worry about that... water will not come in from the side
read this thread post #3 for adjusting clamp pressure...
http://www.forestriverforums.com/for...ps-127599.html
I think you will have good times in your new camper, as have I