Spouse, 40YO/350lbs/OSA but no other probs. Fast ejaculation due to extreme sensitivity-<30sec after penetration. No other erectile problems. Causes?

FATIGUE WITH OSA. Provigil is cheaper and better tolerated than Nuvigil .adderal/Ritalin/Starttera can help. Start a gluten free diet Wholeapproach.com gut loss.com. If CPAP/BIPAP is poorly tolerated seek ENT CONSULT for UPP/ vs Hyoid suspension. ALSO FOCUS ON WEIGHT LOSS. ADIPOSE TISDUE WILL INCREASE ESTROGEN LEVELS, causing ED. Also screen for LowT.
Complicated. Psychological issues as well as biological issues can interplay to contribute to premature ejaculation. Anxiety, relationship matters and earlier learned behavior are some of the pschological. Biologic issues could include thyroid disease, abnormal reflex ejaculation and abnormal hormones. Cognitive therapy, Sex educatin, treating anxiety , exercise, weight loss and sex therapy may be of benfit.
This is normal. Your spouse is out of shape and overweight. He probably cannot run or swim or jump like he could when he was in his twenties. He is able to maintain an erection long enough for penetration and ejaculation so by definition he is successful at intercourse. He will not perform like videos you might have seen. He should take time before and after to allow sex to be more satisfying for both of you.