True story: While working at my empty lot, a "bump-steer" Bobcat excavator rolled a really big tubeless tire off the rim. The owner drove off to "buy some hardware". He returned with a book of matches, and a can of carburetor spray. He sprayed inside the rim, waited a few seconds, then threw a match in the tire's general location. POP! the tire was again firmly on the rim...! The tire was then returned to its correct pressure.
In case I'd left a question mark about using hose clamps to squish the tire onto the bead, here's the hose clamp fix I suggested—as a photograph.
Note the screwdriver. It's sold by Ace Hardware, has four reversible bits (two shown), plus the ability to adjust hose clamps with its 5/16ths inch (or ¼") nut-driver end. While rugged and long lasting, Ace's replacement bits are less than $4.
At least one other larger size of Ace screwdriver is available.
Another way to get a dolly tire reseated is to tie a piece of line around the circumference of the tire, in the middle. Then take a stick and tighten it like a torniquet to compress the middle of the tire and the beads should go out to the rim. Or use a ratchet strap. Only put enough air in to seat the bead, then remove the strap.
The seam can be filled with a waterproof silicone caulk. If you run a weak vacuum at the same time, the seam will be better sealed for it.
"...2) the bailer that broke was metal; there's still a collar which I'll have to break off. Then you think freeze plug will work...?"
Remove every part of the metal bailer. The freeze plug will work. However, so there are no surprises should the plug should get nudged by dock or foot, I'd suggest using a larger washer (than supplied) on the bolt head end. A 5/16" wing nut will enable a quick draining from rainfall. Don't remove it while afloat!
"...3) also got 2 flats on the dolly--which don't inflate with pump so I assume I need to fix or replace inner tubes--but it looks like it will be a job to get tire off the rim (any suggestions?)
1) Check your tires to see if they "read" tubeless. Note the valve stem: have they sunken inside, or firmly wedged in the rim? In either case, try filling the tire again after wrapping several radiator clamps securely in a big loop around the center of the tire circumference. Soap-up the bead with soap suds and brush. You'll be trying to seal the bead on both sides, rather than have the tube (if present) squeeze out of the rim.
2) Tube-type tire: Don't bother fixing the tire. Google around, and you'll find a mounted tire on your choice of rim. Neither rim nor tire you'll receive is the quality they used to be but they're cheap and bolt-on upon receipt. Some require just the removal of a cotter pin. Try Harbor Freight. (If they are lug nuts, make sure the old lug nuts can be removed —use WD-40, "P-B Blaster" or "Kroil" to break the stubborn ones loose).
My bet is that the tire isn't seating on the rim, and your hard-fought inflations are just leaking around the rim.
Edited...:My reply took over 30 minutes, so the previous replies are "still on the mark".
Thanks again. I get to boat in fits & starts. The advice you (& a couple of others) gave me has worked great todate. Cockpit bailer drilled out--and expansion plug installed. Today I caulked leaking seams with 5200. Now remains to fix dolly tires. Sailing will have to wait till next year.
In the meantime, I had a tire loosen from the rim on an old garden trailer with four wheels. A new 5-bolt mounted wheel is now $20! (But watching for a sale).
A new cart is $85.
So I tried the hose clamp "fix" with my 20-gallon compressor.
It didn't work because the tire was Florida-sun hardened, so I drilled six equally-spaced ¼-inch holes into the tread, and filled the inside with Great Stuff®. (Using the remainder of an old can—about ½-full—using a coat hanger to clear the spray head). With the help of the other three tires, it's holding up!