Grinding into 5th and coasting
 

Here is a little history on my car if that helps diagnose the issue. I have been driving the car for about a year and a half.

Since the very beginning I couldn't start in 1st without holding the shifter in place, if I try and take off in 1st without the shifter being held in it will grind and grind and not go anywhere. The solution is simple enough, just hold it in place.
Since the very beginning I had a occasional grind going into 3rd.

A few months after I started my ownership I rebuilt my shifter and put the ford motocraft blend into the car, 3rd gear grind completely gone.

A 5th gear grind just came up and I also hear a very faint grinding only when I am coasting in 5th gear with zero acceleration. This makes me feel like my transmission is on its way out for good. I can double clutch the car to get into 5th without a grind but this is obviously a pain in the ass for daily driving.

My main concern is the faint grinding noise while coasting, is there any solution or do I just suck it up and wait for 5th to become totally trashed and unusable?

Sure, wait. Or replace the gearbox now. It is 110% boned