I am using a camera connected directly to a monitor to reduce lag. This allows me to see both the monitor and the board at the same time, without moving my head. I see the board an the tip at an angle allowing me to judge the height. When soldering, I will mostly look at the monitor and regularly scanning to see the height of the tip.
The bigger problem is with placing fine components on the board. It's just slow and irritating. I will position the component in its location and then slowly bring it down until it touches the paste.
Have you tried not using solder paste and instead using a "normal" thin solder wire (with jelly flux)? I prefer to use that over solder paste for everything up to 0402.
Reflow seems to be much easier for me as I can take multiple tries at placing the flux paste and then the component and then once I'm happy with the placement I no longer have to touch it and instead hope surface tension and solder mask will do its job.
Takes more work but with my eyesight, no stereoscopic vision and limited motor skills I am pretty happy I can do it at all.
A TL;DR:
1. Binocular microscope to see depth.
2. 4" or greater working distance, achieved with a Barlow lens, not <1" as on other microscopes.
3. The best and brightest ring light you can afford.
4. Stable mount.
Also, with regards to #3, I found their recommendation of LED ring lights odd:
> At $30/each and requiring us to keep a few in stock in case one blew, we found that although halogen lights made it easier and clearer when examining motherboards, the reliability, flexibility, and low operating cost of LED lights prevailed in the end.
Surely $30 every 3-4 months is a tiny fraction of what their work is worth. I pay that without hesitation, because the light is just better. Also, the 200W heat of the halogen bulb is far away, at the end of a fiber optic cable, while the 40W of LED lights is right under my eyes and near my hands, and I have a gentle fan to move soldering fumes away so only the latter is bothersome.