How long can I shower with tub chips?
That looks to be a porcelain tub painted over with an epoxy paint that was not done correctly.  An epoxy paint over porcelain requires proper preparation of the surface.  This does not appear to have sanding done prior to application.  So best recommendation on a low budget is to buff with a tiger disc all the existing epoxy.  Then clean extensively to remove soap scum and contaminants on the porcelain surface.  Then call a qualified porcelain re-finisher to do a professional job.  If this is a fiberglass tub,  do the same as above and call a fiberglass re-finisher to do it correctly.  Or replace the tub.  Mold and rust are not something you want in your home or in your body...