You can fix this with just a standard pair of pliers.
Use them sideways to put pressure on both sides of the lock nut to release the pipe.
After the fitting is completely removed, run the pliers around the pipes to scrape the paint off (DO NOT squish the pipe at all). It looks like it will all come right off, if not, finish with an abrasive.
If it still leaks, you've messed up the fitting; get a new one. If it still leaks after that, the pipes are likely deformed. At that point the easy fix is over and it's time to sweat it. Or you can keep cutting bits off to get a better connection and trying SB connectors: you'll need a length of pipe to make up the difference and some straight couplings.
Check that fittings and pipe are clean, in good
condition and are free from damage and foreign
objects. Cut the pipe so that the ends are square.
Ensure that there are no burrs or damage to the cut
end. Wherever possible proper pipe cutting tools such
as rotary pipe cutters (copper tubing) or pipe shears
(for plastic pipe) should be used.
– sharkbite.com, pdf
Crap inside the pipe doesn't really matter; they're talking about the OD: "in good condition and are free from damage and foreign objects."