Obviously working off the same information as you, but it sounds more like he stopped him from leaving during the winter, and didn’t stop him after. Kitty made his choices and regrets them now.
The cheap flee collars do not work, and if the cat was even semi-feral good luck getting any collar on it. Tropical is usually best, but stuff that works is also not cheap.
What does work are anti flea drops you put on their neck, where they can’t reach. Lasts a month or so and kills fleas and ticks. My mum’s cats are outside a lot and they never have fleas or ticks, when my mum doesn’t forget putting the frontline drops on.
Yeah that's what they referred to as "tropical," a misspelling of "topical." But as they say, it isn't cheap for the good stuff. Frontline doesn't even work in my area, gotta be advantage II or revolution.
You don't let a cat outside when it wants to go outside, their instincts tell them they need to survey everything they can see, my cat is EAGER to run out the door and then he gets outside and is terrified and wants to go hide. Not every cat is terrified but once you have an indoor cat, it's an INDOOR cat.