For the pivot housing plugs, what I've done is put OMC/Evinrude gasket sealer on the threads, for the pivot housing plugs they don't have to be super tight to seal as long as the o-ring is in place. I've been doing it that way for 18 years and my boat is in salt water 6 months out of the year. The OMC/Evinrude gasket sealer stuff is like magic. They will come right out next time because the sealer keeps water out. If you're having to use an impact screwdriver either sealer was never used, or they were overtightened.
For the drain/fill plugs they only have to be tight enough to seal, and if you use a new fiber washer (white ones) each time you don't have to worry about leaks. No sealer needed here. There is a newer style drain/fill plug available for the one at the bottom of the lower unit and the next one up, they are actually for Evinrude outboards but fit perfect and use an Allen recess. Easier to get in and out. The top dipstick one, if its all chewed up you can replace it.