Drivers side is bulging, so deffo chassis rail will have rot, there's still plenty of strength there.
Up to you if you dig, the rail is a U section, the plate you see that is bulging joins onto the inner sill, from memory, I'd bare metal it, find and drill spots and carefully removed it, this will leave you looking at the underside of the rail.
They'll be some big bran flakes and the rail will be slightly holed and thin, cut out the weak metal, repair it and plug weld the saved outer plate back if it hasn't suffered too much.
You'll have to drill out the spots for the jacking point and remove it as it's welded to the above mentioned outer and then onto the inner sill.
I'd tackle that drivers side mount first, leaving the jacking point off and obviously not welding to the inner sill until you've put some new metal in.
The jacking points will save easy.
Remember, drill out the spots, pick it apart and it'll all make sense, deconstruct it carefully, don't welt into it with slitting discs and cold chisels throwing out good metal having to buy replacements , all you'll need is a pair of outer sills and some 1.2mm sheet, I'll bet inners I'll need rearmost a couple of inches letting in and a few areas towards front jacking points.
Good luck.