What is enviro-safe composed of ?

Why do you think that would be better than 134a ?

Oil loss with a leak depends on where the leak is... if at a low point oil can be lost.

Normal depressurizing and refilling does not affect the oil amount in the system enough to worry about. But since you may well have had oil loss .... as evidenced by adding oil affecting the noise you heard... the only way to be sure you have the correct amount of oil ( that I know of ) is to flush and measure what you put in.