Well, welcome to the world of boat ownership... I assume you've heard the expression: "A boat is a hole in the water, surrounded by fibreglass, into which you pour money!"?
It sounds like you have a few little issues to deal with! Starting with the easy stuff... I suspect the "trim tab flappy things" are what are referred to as "elephant trunks"... they're drains. Do they have a piece of line through the end which runs up to the transom someplace? If so, snug 'em up and they keep water out. Let them down, and they drain water... as long as you're moving! (Sounds like you need them at the moment!)
The leaking valves probably just need a clean and a lubrication. Not being familiar with that particular model, is it possible they have an overpressure assembly in them? If so, these will leak as the tubes warm up.
As for the tube being loose... do you mean "loose" or "off"? If it's loose, how does it look like is attached? Someone with a similar boat while chime in eventually with the solution! The flap on the bow sounds like it needs to be re-glued. The solution to this will depend to a large extent on the fabric. I doubt your boat is hypalon (which is infinitely glueable) but more likely Strongon or some other welded fabric. This can be repaired, but might require some professional help.
Incidently, did you not notice these loose/unstuck items before you bought the boat. If not, that suggests they are probably fairly minor.
Don't panic... One of the great things with inflatables, is that they are generally easily repaired, often by the owner!