I have a feral that I have cared for for a few years now, although she has lived in my neighborhood for 5-7 years, our best guess. Someone got her TNR'd, thankfully. She would not even take food from me when I set it next to the garbage cans at night, for YEARS I tried. Finally, one day, she took the cat food. Then started coming back daily for the food, which I slowly moved closer to my door. The first time she came onto my porch to eat the food, I sat in a chair and she belly crawled to my door and shook all over the entire time, inhaled the food and fled. But she came back daily. Within about 2-3 months, she started to groom herself in front of me and sit down, she'd stay about 10 feet away from me and I ignored her, sat in a chair reading a book. Another few months, she started to come closer to me, rub her chin on the side of the house by the chair I was sitting in, wanting SO bad to rub against my leg. When she finally did, it was about 5-6 months after she began accepting the food, she finally did rub against my leg.
We made baby steps the entire way. Me, I just let her always come to me, I never made the first move to go towards her. It was probably close to a year before I could scratch her head and her chin, which she LOVED, but she would try to smack me if I tried to per her on her back. But one day, she finally let me. Now, I can pet her all over, even her tail, while she is eating. She does NOT want me to pick her up. When I tried once, she didn't try to scratch or bite me, but she freaked and squirmed to get away, so I don't try. She will let me sort of half-pick up her front legs, but it took a LONG time to get to that point. Like I said, the whole thing has been baby steps, with her being the one to come to me. If you keep feeding Heck some good stuff and just be patient with him, he will come around. Trust me, he will. He may never let you pick him up. But he will come around. You are so far beyond what I was with Arwen after a month. Heck will start to trust you more. A month is such a short time with a feral, they take a long time to gain your trust sometimes. Obviously, your Heaven is a little easier, but they are all different. I would just say, don't rush things. Be totally patient. Let him come to you. Let him know that it is all on his terms and you are not going to try to corner him and make him have any affection unless it is on his terms. Arwen hissed and growled at me for MONTHS when she would come up to my door for her food. She would hiss, growl, then scarf her food and run. I remember when she finally stopped hissing at me, and started mewing instead. Every step has been wonderful. I adore this cat so much, and would love to have her in my house, but she won't even consider coming in, and I have 3 inside cats already. She is allowed in my garage, but she doesn't usually stay there. Luckily, I am in FL, but I do have a heated cat bed for her on my porch.
I wouldn't continue to make eye contact with him. Not yet, at this point. You just want to sort of be there, non threatening in any way, even though you don't mean to be threatening, he probably doesn't know that yet. Just sit quietly around him, read or be on your computer and hang in the room with him. He will get used to you. I believe he will get to that point where he approaches you and wants to be near you and maybe want affection at some point, but it's going to take a while.
Now, more than 2 years since I started gaining Arwen, my feral girl's trust, she finally trusts my husband, one of my neighbors, and lets them both pet her as well, something I NEVER thought would happen. She used to only be seen on garbage days, at night, that was the only time you would see her.
Thank you so much for taking care of these poor little things. You will gain their love and trust one day and they will love you so much for it. There is nothing like the love I have for my Arwen.