HI there... I dropped the morphine within a day. It gave me nightmares and I had a restless sleep and woke up feeling blurry and unrested. Is he in pain? If he's not try seeing how long he can go until he begins to get uncomfortable. With his type of surgery I'd be willing to bet he's more numb than in pain. Though everyone is different. Also depending on how much food and fluids he is taking in the morphine will effect him differently (kinda like taking drugs on an empty stomach)

Drooling is par for the course and depending on how you sleep you can choke on it. Tell him to sleep on his bad side with a cloth under his head. That way the drool is less likely to trigger his choking response and the drool will pool and run out onto the cloth. Everyone has to figure out what works best for them but this may help. I have chronic post nasal drip from rads when I sleep I still favor my bad side that way I can't "feel" it during the night.

as for the stitch it depends on the surgeon. My surgeon removed 30 - 50 % of my tongue. he also removed the floor of my mouth on that side and rebuilt it with the skin right up to the gum line. Because of this I actually have a fully formed tongue that is very adaptive and moves well. In fact my speech is completely clear except for when I am tire then I have a slight lisp.
Some drs actually tether the tongue in place (why? - is beyond me) If this is meant to be permanent, once everything is over and he is feeling better maybe they can adjust it.

Hugs and you're amazing.