I think the kitten I adopted was mistreated and i am upset as hell. Any resources?

My partner and I adopted a kitten today. We adopted one last year, and decided to expand to two over the long weekend to be able to supervise introductions etc. We adopted from a woman whose cat had apparently had an unplanned litter and the kitties needed to go, and this sweet boy was the last of his litter. However, upon settling down in the car on the ride home/arriving home we noticed many things.

1. He is so small and skinny for 18 weeks

2. He smelled of urine and poop

3. He has fleas

4. He's crusty? As in crust on his ears and nose etc

Now we're home, we've spent the day doing a very difficult introduction to the resident cat (1.5 yrs siamese mix) who needs tons of reassurance he's not getting replaced, along with quite a bloody bath for kitten, flea treatments for both and setting up bases. Kitten is extremely skittish, wants pets & play but hisses at the same time, seems to absolutely hate having the lights on. While I'm sure this will all get better over time, I'm just increasingly upset at the woman who gave us this sweet child. Why would you not spay your cats? If you're not going to take care of their kittens properly?

When we went to get him we saw these things and there was no chance of me leaving the kitten where he was, but also no chance of me arguing with this woman in her own home. If there were any other kittens there they would be HERE WITH ME. It's infuriating though, and nothing can really be done/I am unaware if there are resources with this kind of thing. At this point i'm fairly convinced she is just breeding her cats on repeat for profit(?) and not taking care of them in the slightest and I wish I could make sure this has an end. Are there any places to call to report this kind of thing? Would the SPCA/local organizations have any authority there? (We are in Canada for reference)

Thank you:)

PS would also take recommendations on making introductions easier for our resident cat who is anxious as all hell right now and never liked treats so i can't bribe him