Accidentally started taking care of a feral cat colony

I'm a college student visiting home for summer and have taken to possum watching on the ring door bell log. I realized while possum watching that we have a feral or stray cat coming to our porch every night and just hanging out. I decided to put out some food for it in hopes of being able to eventually tnr it or maybe even get it adopted if it's a stray instead of being feral (it seems under a year old). Unfortunately I did not realize that putting this food out for the cat would cause a feral colony to form in my front yard. We now have about three cats that visit nightly. One of the cats seems to be in poor health and I hope to get it to a vet soon. The other cat seems like a lost cat, it's very friendly despite being a bit skittish. The two new cats seem to be mating so I am going to try to tnr them soon, the only problem is my possum friend keeps coming before the cats and I'm worried about continually catching the possum and scaring the cats off in the process.

My dad was all for feeding the first cat but now that multiple cats are coming to the porch he thinks we need to stop, he thinks they'll start going to the back yard instead and will attack our cats (our cats are indoor cats with access to the backyard, they have never attempted to leave the back yard). I don't think they will as the fence is high and the yard backs up to a loud busy street which I doubt the cats would want to be near. Ive continued feeding the cats and have put out a cat shelter since it's tornado season. I know that now that I've accidentally started this feral cat safe ground that they now rely on me and I can't just take away their sources of food, especially when they all look to be starving.

My point in posting was mainly hoping for some advice based on this situation. And wondering if anyone has experience with having feral cats visit their front yard and if they will try to come to my back yard. I know it's recommended to not leave a bowl out all night but the cats won't come for a specific feeding time and the youngest is too scared to come at the same time as the other two. They also come frequently through out the night from 7pm to 5am. We don't have any racoons near by to mess with the food, only possums which I know don't carry many diseases. I'm also worried about the possibility of these cats luring coyotes to my house, as coyotes do live in the area, but I haven't seen any in my neighborhood in months.

Thanks in advance to anyone that reads this much.