Pasteurization is a pretty cheap way to go about it, what quantities are you working with, pony keg? There are some new wine detectors that claim to measure free sulfurs in barrel during aging. But they're pretty expensive. For the price of the glassware to run free sulfur you can buy 3-4 really good sous vide devices.
There are tables that show safe levels of fso2 with %alcohol and ph on x and y axis. Should be easy to Google.
Do you have a digital pH meter? You could theoretically do free sulfur by watching the rate of pH change during.... I forget the chemical it's been a number of years since I did the wet chemistry, sodium hydroxide I believe... addition, once the pH spikes, it's how my old lab currently does it.
If you don't have the equipment and aren't doing large quantities, it's not worth the investment, pasteurization is very easy to control, I'm not sure how it changes the profile (I'm a chemist not a taster/maker) that's the easy route, might not be the best taste, but it sounds like you're a home brewer, longer lasting is a fair trade for a little bit of flavor, and you won't find any skunks months later.
Edit: Sorry I just realized you don't need glass ware (outside of a flask and a graduated cylinder) to do free sulfur by the ripper method (as long as you're making a clear-ish product), you'll have an error of 5ish ppm, and a drop or two of iodine to 25 mLs of your product, then add NaOH until your iodine does it's iodine thing (turns black and stays black), measure amount of sodium hydroxide used, so some quick math (it's a simple multiplication equation once you have your concentrations and quantities) and you'll have your free sulfur number. Those lab chemicals and glassware will probably be about the same cost as a sous vide.
But man I swear by my sous vide, mash potatoes, stew, meat, there's almost nothing I won't cook in there (some of it gets seared after cooking)