1) Cut it off and replace it with Quest compression tee.
( Don't use those for your house, but they ok for campers)
2) "Ring busters" are available, but they main goal is to
save the fittings ( you don't need one )
3) It is easy to replace PB with new PEX and most places
carry PEX to PB adapters. PEX is just as flexible as PB,
and have similiar flow. So replacing PB with PEX is no brainer.