Thank you; this puts things in perspective. (I am not the right kind of autist to draw lines and angles all over a photo of Jack in his kitchen.)
Looking at the geometry exhibited, I think Jack
could hold a urinal over his urethral opening while in a wheelchair. The problem would be getting to it.
The confounding factor, besides his body habitus, is the sitting position. From my experience with naked aging fat men, he does not have enough free penis accessible to pull through the slit in a pair of briefs and then a trouser fly, much less over the top of sweat pants.
Healthy male urinators may argue, but please consider that you are imagining pulling your clothing down while standing. Jack is in a sitting position, with dubious leg strength/control. He is sitting on his pants and underwear and holding them in position.
After that, the problem is his single hand. If Jack could get a nub of dick exposed, it would rubberband back into his clothing when he let go to pick up the urinal.
As a veteran of elderly debilitated voluntarily-incontinent fat people, I predict Jack will discover external urinary catheters, although possibly not until he is at home and in Tammy's 24/7 care. Not a texas cath, for obvious reasons; probably the
dick daisy Men's Liberty, for its design and for its mighty daytime TV advertising budget.