If you have hearing loss and must turn up the earphones, doesn't that make you have more hearing damage faster?

Yes, if over 85 dB: Government guidelines limit occupational exposure to industrial noises over 85 db. Some personal stereos pump out well over 100. If your ear buds are distracting those around you, then they are definitely too loud.

Theoretically yes: Hearing loss if more than 80 db loss it considered severe. If you have a hearing aid that has sound intensity of more than 80 db them it is likely to stimulate what ever intact hair cells in the cochlea, and make you hear better. It is possible theoretically to damage these cells subjecting them to intense sound.