glad you finally spoke up!!
i can't answer all your questions, but you might help convince your mom about the hive by pointing out the increased yield in her garden from having the bees around. your spray question probably depends on what kind of spray he uses and when he sprays. there are sprays i use that will not bother the bees as long as they do not come in contact with the spray. i spray late or early when the bees are not around. dandelions are great for bees, but not so great mixed in with your hay. guess you can't have it both ways
try for at least 2 hives. that way you can use one to boost another if you need to. it's to easy to lose one just because you can't rescue it with brood, etc.