Hi again, Ewan.
You mentioned about the snake crushing bones when constricting prey; this is true, but I don't think the shoulders would be crushed, because the snake would be wrapping itself around the torso, mainly, and would be trying to unhinge it's jaws to take in the body. It would not be able to, for the sake of this scenario, constrict the guy from the shoulders, down, if it starts to ingest the guy from the feet, first.
1) How long will it take the snake to swallow the guy up to his thighs?
--This would be a slow process, so probably a couple of hours.
2) What would the snake think when it reaches the area covered by the guys very brief small black swim trunks?
--The snake will not notice them, he will just keep taking the guy into his mouth.
3) Would the snake have any trouble swallowing the area in the small black swim suit?
--No, the snake wouldn't have any trouble swallowing that area, it would be just like the rest of the guy's body, to the snake.
4) What would the snakes owner think when she saw the snake swallowing up the area in the small black trunks?
---She would feel sorry for the guy, but be glad she was able to feed her snake; it would excite her.
5) How long would it take the snake to fully swallow the guy, if all the possible problems with the guy’s shoulders were solved?
---It would take many hours; maybe 10-12.
6) You say it would take 3 to 5 months for the snake to digest they guy, what parts of him will be digested first?
The flesh would be digested more quickly and then some of the bones.
7) What will happen to the guys small black swim trunks in the snake’s stomach?
---The small black swim trunks will be slightly digested, but most of the material will come out in the snake's waste.
8) Would the black trunks cause the snake any digestion problems?
---Yes, it might cause a slight blockage, but the snake would eventually pass it.
9) What if anything would be left of the guy after digestion was complete; would anything be visible in the snake’s droppings?
---Yes, the swim trunks, as I mentioned, and bone shards would be visible in the snake's droppings.
10) If the snakes owner , while watching the snake swallow up to the guys thighs , decides that she should not let the snake swallow the small black swim trunks , what will she do ?
---There would be no way for her to remove the swim trunks, since the guy's body, up to his thighs, would be in the snake's mouth; however, if she moves fast, and carefully, she might be able to cut the swim trunks off before the snake takes them into his mouth.
I hope this helped!