How are you checking tonearm level?

I’ve been listening to the way my TT was setup when I bought it about 18 months ago, but am now taking a closer look and my the cartridge appears to me to not be parallel. Twin parallel lasers? I can’t spot 92 degrees.
‘VPI Prime Signature, Hana ML low output cartridge.
It doesn’t need to be parallel! You can play with the "rake angle" by adjusting the tonearm height! The cutting angle of LPs has always varied! By adjusting the rake angles for different LPs your cartridge can more accurately trace the grooves!
Rake angle is judged by a side view of the cartridge. Azimuth is judged by a front view for perpendicularity to the LP surface.
The visual angle you are talking about is the crudest, the biggest of ballparks, like you have no idea. It is not btw tone arm level, that is irrelevant. Technically what matters is SRA, stylus rake angle, the angle of the stylus in the groove. The stylus however being so small we usually go by VTA, vertical tracking angle, which is what you mean by tone arm level.

In any case, whatever you want to call it, the real goal is to precisely match the angle of the cutter head that cut the original pressing. Because this way it will track the groove most precisely. If the angle is off even slightly then the stylus never will have a chance of precisely following the groove. It will be like trying to poke a stick in a hole with the stick not lined up with the hole. It never will go all the way in.

I'm sure we all know how frustrating that can be. 

Anyway, this is one where the only way to be sure and get it right is to play a record, adjust VTA very slightly up or down, and play the same record again. If VTA was too high to begin with and you lower it down the sound will become more full and yet also more detailed. Keep lowering it down, a little at a time, until finally one more drop and the sound gets fuller but instead of detailed it actually loses detail and becomes slightly bloated. Then go back up to where it sounds best.  

By very slight adjustments I mean tiny fractions of a millimeter. Depending on how far off you are in the beginning you could lower it a millimeter at a time, until you are too far one way or another, then titrate to get to the right point.

Now you see why visual reference is so crude, and why VTA on the fly is such a nice feature to have.