You worring way too much. first - if it low it's leaking so take care of leak first. After reading all the material presented by Lucky1 and figuring your reading mistake.
My suggestion is:
drum roll please!
Based on it being a daily driver (dd)
And money tough to keep.
And they (dex and ATF+4) are ATF fluids in similair circumstances.
Did I mention reading with open mind all the Lucky1 thread ?
I assume the converter is not shuttering on lock up EVER.
Add ATF+4 to bring up to snuff and start getting some of it's benefits.
unless you got the $ stash to go the whole route.
Got cash? Do this! a flush procedure that will work at your shop/garage/driveway.
Remove rear cooler line at tranny and slip a drain hose on and place in 3.4765 gallon catch can. Start engine and let idle while shifting (mostly neutral) through gears. When fluid starts sputtering out of line, shut down immediatelly. Now drop pan with no leaky mess and let drain by loosing the 7/16 bolts 3 turns or so and gently pry valve body down. This procedure will drain all but a quart or so of the GM stuff in couple hours.
Adjust bands, install new filter, Retorque vb
bolts and isntall cooler line. Reinstall nice reusable pan gasket unless rebuilder too cheap to buy when building.. Secure gasket if needed and make sure gasket surface on pan not dimpled. Straighten if needed. It will probablly take 12-14 quarts to fill and be on your way.
I would do the latter of suggestions, cause I a butt about doing things right.
Glad we got that straighten out.