Oh dear...
The first question that popped into my mind: Is it playable, and more importantly, does it feel nice?
If the answer is yes, then the next question is: Does the angled fretboard matter other than that it may not be identical to that of an original LP?
If the answer is yes, how about accepting it as a feature customized according to the preferences of the player?
The biggest issue with lacquer on the neck is that it becomes sticky when your palms sweat. For what I've learned about Nitro is that one of the main features of it is that it can be applied very thinly so using it as a transparent filler seems illogical. A thick layer of lacquer of any kind may start cracking which can be very inconvenient. Lacquer fragments in your palm don't feel nice!
If the edge of the fretboard really is so sharp it's uncomfortable to play, re-shaping the width or cutting the neck off and replacing it are the only viable alternatives if your goal is a quality instrument. For reshaping the existing one, squaring the edges and binding the fretboard would look nice, but instead of lacquer or nitro I'd use wood filler and paint the neck - and ruin the nice looks of mahogany! Also bear in mind that wood filler can crack as well as lacquer or nitro. Anyhow, painted necks have been around forever, hiding the most beautiful pieces of wood.