Penicillin isn’t just growing some mold, it was selected for out of literally tens of thousands of strains of mold that were sent in from around the globe to find one that wouldn’t kill the patient. You would, at a minimum, need: microscope optics, glassblowing equipment to perform extractions and purifications, a source of solvents (ether will only go so far), assaying equipment (even old school stuff needs indicators), and enough industrial progress to make and machine steel to be able to scale any of it up.
Just finding the correct strain of mold to begin to produce any form of antibiotics would need a pretty insane amount of hardware to make what we would consider a rudimentary lab in modern times, let alone isolating it in a way that’s safe for human consumption.
When you lose weight that fast the fat around your body isn’t removed equally, and you still have the extra skin left once the weight is gone. It takes a few months to a year to have everything even out.