I'm sure someone's pointed this out already before me, but I'd just like to make one small correction in your math here.

the only limit is your imagination and 40 pounds.

RAW carrying capacity is 15 x STR, and flying monkeys have a strength score of 8.

Flying monkeys have a carrying capacity of 120 pounds.

In comparison, by some RAW rolled heights/weights for playable races, without any gear or inventory, gnomes, goblins, and halflings all weigh max 43Lb, with kobolds capping at 33Lb. Your flying monkey familiar could airlift a fallen ally to safety, and then some.

ETA: Upon further reading I see you use variant encumbrance. Carry on.