Just screw the new stud in finger tight until it bottoms. You can gently "snug" it with pliers (use two jammed nuts to protect the threads), but there's no need to forcefully jam it.

If you were nearby I'd yank a few studs of an old engine for you. The waterpump is certainly NOT a demanding application.

If the gasket is new and undamaged, I'd reuse it, but I't first give it a light coating with RTV. I prefer red (hi temp) RTV.

I don't bother with a torque wrench even though I have maybe 6 of 'em. I just snug up the waterpump nuts 'n bolts 'til they feel about right. Never broken one, never had one leak, done dozens 'n dozens.....

If your torque wrench doesn't feel right to you, then perhaps you should try a different one. Yours may be whacked out or broken (it does happen...). It's easy to test one wrench against another with a square drive adapter. You can also attach a 1' arm and hang 10 lb. from it -- that produces 10 lb-ft of torque if the force is perpendicular to the arm. In other words, the arm MUST be exactly horizontal.
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Don Foster (near Cape Cod, MA)