One of my only households with pets I play with consists of two adults and two young adults, one toddler and two dogs. I've only had one time where I had to go to the vet, and it was because I triggered it by going there with a different household I think. The oldest person there seems to also be the only person getting sick often instead of the dogs. Maybe try repairing your game? I don't think it should happen everyday :#
Mine don't seem to get sprayed often, they just get dirty more than I'd like when they go out (but it's more manageable I think in comparison?)
The only ones that are pretty unhappy in the house is probably the toddler since her dad keeps hanging out with his sister's dog whenever he gets home, but she's starting to fill out her skills so she's more independent now so she can do things herself 'cause both her parents are pretty bad LOL
The resetting might be linked to CC if you use it, since some couches and stuff do that. S4S has a batch fix for those so you can fix them. If not, DeKey's suggestion of playing on speed 1 works, especially with bigger households.