Can I clean razor blades with isopropyl alcohol? I bought gillete Mac 3 disposable razors. Should I throw that razor away or use it till it's dull?

OK to keep using it. Disposable razors are designed and intended to be used repeatedly until they become too dull, and probably almost all men do it that way, without cleaning or disinfecting them. If you have no obvious skin infection in the shaved area, and if the razors are not shared with other persons, there is no health risk.