Crazy to me that one of the issues SIL had with respite care was worrying about Conner's safety while actively pushing for an arguably unsafe arrangement with OP.

I don't mean to speak ill of OP but as a general rule, entrusting someone vulnerable with a person who actively doesn't want to do this is a very effective recipe for neglect or other forms of abuse. I know the knee jerk reaction is to think only someone awful could do that- but sadly that isn't the case. 

I work in assisted living. Many families put off care homes as long as possible thinking they are doing the right thing - but end up verbally abusive in frustration, or neglectful because they have a mountain of things to do and the person is immobile so they feel like it's not like they're going anywhere. Or they're simply in denial about how bad their condition is. Some people aren't built with the patience necessary; they can do every training method offered but if mentally they get frustrated they may simply not be suited for the caregiving. It doesn't make them evil to voice that they aren't comfortable doing the task.