What I would do is this: Run the injectors as-is for a few thousand miles. Then remove them, and find a shop that can pop test them (just pop testing takes like 15 minutes and should be cheap). If they test within 5 bar from highest to lowest, and you can't find a shop to do the balancing at a reasonable price, just leave them alone. While it would be nice to balance closer than 5 bar, there is not a huge improvement from doing so. Now, if the difference is more like 7-10 bar (or worse!)... then I would at least have the worst offender(s) re-shimmed to pull them back into spec.

You might consider buying a pop tester and shim assortment... you can probably locate a tester for $200-$300, and a shim assortment for ~$100 or so. Then you can do it yourself, and either keep the tools, or re-sell everything to another forum member when you're done to recoup most of the $$ spent.

In general I don't recommend using ATF in an indirect-injection (prechamber) engine, nor any sealants designed for transmissions. I'd use a healthy dose of Red Line DFC (or 85+) instead (like, a full bottle to half-tank of fuel, or something like that). Fuel leaks at the IP are often the delivery valve seals, which should just be replaced, it's not that difficult. FWIW, when I change the main fuel filter, I usually fill the new filter with Diesel Purge. But let us know how the ATF trick works out.