Is the cat spayed or neutered?
If not, then do so.
It can affect behavior. Neutered cats typically being less agressive.
2) The cat could have anxiety/neurological problems. So see a Vet and meds can be prescribed to help the cats moods. Anti-anxiety meds etc.
3) Cats are territorial. The cat only knew your Husband. It is your Husband's cat. Your daughter is a direct challenge to the cat's territory/home and your Husband. Hence peeing.
The cat is trying so hard, to re-claim his/her territory and his/her place in the family. And the cat probably knows, you do not like her/him. For sure.
4) Per fleas, you also have to treat the outside and the cat too ALL AT THE SAME TIME. Or the fleas will recur. Just bombing the house will not get rid of it, if the cat is still going outside or if the cat does not have a flea collar etc.
Fleas were probably gotten from outside.
Our pet rabbit once, got fleas. BECAUSE, we used to let it outside on our lawn for exercise. BUT it got fleas. It was not the rabbit's fault. The neighbors, have dogs outside in their yard.
Does the cat, have ANYTHING or anywhere that is JUST ONLY his/hers??? If not, then the cat deserves to have... a cat bed, toys, perhaps a wall climbing thing or scratch post etc.
Who feeds and plays with the cat? Only your Husband? If so then of course the cat is not going to like you, because it knows you do not like it. And now your daughter is first.
Have you ever fed the cat routinely or played with it? Or give it treats/food??? Cats like routine. And they like to have their own area.
I would highly suggest, taking the Cat to the Vet, to check for neurological/anxiety problems. If this is the case, you cannot blame the cat. As you said, the cat is or always has been, anti-social. It probably has anxiety issues.
And the cat, is only comfortable with your Husband. That is how many pets are. The "owner" is their owner. And trusts their owner, the most.
If you get rid of the cat, your Husband will be put in a real bad sad position.
I have had cats and all sorts of pets.