Questions about age, adjustment time and eating.

If your following all the advice people have given you in this thread, I cant think of anything else. Others might.
But like I said, sometimes it just takes time and patience to get a live feeder to take F/T.

I have always had pretty good luck switching over to f/t with snakes that have had live with previous owners. I try to emulate the movement a live rodent would make as much as possible. I let it actually touch the floor to create the vibration on the substrate. Instead of wildly jiggling it, I do a couple subtle jiggles while moving it, let it be still, a couple jiggles, let it be still. I try not to have the rodent "facing" the snake, and find that reluctant feeders will almost never strike if they think the rodent is looking at them. They prefer to come in from the rear-side angle and get the neck in an unsuspecting rodent that just walked past them. The distance between the rodent and the snake I get a lot more variance what is preferred, but about 3" away from the snake seems to be good for most.

You may have better luck keeping him on live for a while until he is on a schedule, and then trying to switch, rather than going right back to f/t after one successful live feeding. I generally go straight to f/t when getting a new snake and stick with it even if they refuse for a good long while, but if I resort to live, I stick with it for a month before trying f/t again. Since you have already tried to do f/t again, I'd stick with f/t for at least a month before giving up. The last thing you want to do is condition him that if he refuses f/t, he gets a live.

Too small is almost never a problem as far as whether or not they will eat it, only in whether or not it's getting enough to sustain it's growth. After fasting, a bit on the small side is a lot more likely to get eaten than what you would normally feed that size of snake. A pup would be the appropriate size if he was eating regularly, you may have luck trying a fuzzy instead.

A healthy sub-adult can easily go months without eating without any issue so try not to stress too much about it.

If he’s only been with you for about two months, and has eaten in the past 10 days, I see no reason to worry. The snake is over a year old so it definitely knows how to eat. No healthy animal, including humans, will starve itself to death when food is available. My method for picky eaters is very simple. It doesn’t matter if I’m switching from live to f/t or from mice to rats. The formula remains the same. Keep offering food every 2-4 weeks until the snake decides to eat and they ALL eat eventually. You can try all the zombie dancing, scenting, braining, and switching prey type tips and tricks but the bottom line is the hunger ALWAYS wins in the end. I had a young carpet that took about 4 months before she started eating consistently. Now she never misses a meal. I’ve had two BPs go 8 & 12 months without food and they were both just fine. Make sure your temps are dialed in and try to enjoy your critter without stressing about it eating. I know it’s hard but I promise it’ll eat when it’s ready.

EL-Ziggy is spot on with advice. Hunger will turn him eventually.
I think you are worrying too much about not feeding every week. That was the hardest lesson for me. Sometimes continually offering food when they dont want it can be a stress and put them off. Let him chil for a bit.
They don't get food every week on the same day in the wild, sometimes they have to wait a number of weeks for food, they have evolved for that.
I have waited months sometimes, and then when they are ready they become raviaunas and regular feeders.