Safety might be perfectly ok - just assembled incorrectly.
There are several "start" positions to the thread in the two halves. Only one is correct and gives the correct crisp action, most give a safety that obviously won't fit or work - but one position is wrong but appears to be correct. This last "wrong" assembly is - in my experience - responsible for about 90% of "safety problems" where people consider changing the spring.
Briefly, the two halves have to screw up into an "11 o'clock" position relative to each other. If the two halves are at "quarter to twelve" or similar,then the safety is incorrectly assembled.
Here, the left safety is "wrong but works badly", the right safety is correct:
https://www.milsurps.com/images/impo...72349296-1.jpg
Re: rear sight slide. You don't mention the condition of your rifle (maybe post some photos?), but its common for many rifles to have an accretion of oil and dirt built up in the worm gear track on the right side of the slide, as well as the adjusting wheel itself. Try scrubbing these parts with a wire brush - use some powerful solvent or paint stripper if there is a thick accretion (careful not to get this stuff on the woodwork).