No need to cut the pan. The relief valve needs to be plumbed separately to a place where the discharge of hot water under pressure will do no harm, ie: through the floor and belly wrap into the crawl space. You will need two holes through the floor or wall. One for each drain. You don't want the rel...

Yes, check with zoning/building/codes office to get the straight scoop.

It sounds like the caulk you have is old, and almost dried out.

You could build a new peaked roof over the two, but you would probably have to support it with poles set outside the trailer walls on proper foundations, below the frost line. Kind of a pole barn type structure. The home's walls/ foundation will not be strong enough to support the new roof structure...

It looks like your tub is plastic. Make sure it is adequately supported underneath to withstand any flexing from standing, particularly around the drain, so cracks don't develop.

I have the pb pipe in my home, and the only trouble I have had was with connectors that were under stress. And when the mouse decided it was an appropriate tooth sharpener. Do some research on pex pipe and connectors. I have used it to fix leaks, replace under sink supply valves, etc. It is very qui...

Do the whole thing.

I believe you are on the right track. It sounds like the installers did a poor job. The intake hose definitely should go outside, and the existing holes should have been sealed.

You could use a borescope and make a small hole in the ceiling, or maybe through a roof vent. You can find them cheap on Amazon or Ebay. This is assuming you have an actual attic space. If you have a furnace with a flue up through the roof, there may be an easily removable ceiling panel in the furna...

The yellowing is caused by, or at least sped up by, sunlight.

Have you sealed the gap around any pipes that penetrate the floor, such as waterlines and drain lines? Air movement is your enemy.

Looks very nice.

Call a pest control company. There is probably a spray they can use that will have a lasting effect.

Hmmm. Just a wild thought here. Pour footers for your "poles," so that the wood is above ground. Use treated posts, with adequate spacing and beams to support the roof. Maybe even steel I beams? Set your trusses over the peaked roof height. Extend the exterior walls to the trusses, then re...

Well, you could do a ridge beam with a salt box style roof. That would keep the peak lower. Or you could rip off the peaked roof and use trusses. And you are absolutely correct in the pole barn style to keep the weight off the walls.