Blind harlequin tuskfish

I got a harlequin tuskfish from my LFS which uses copper in their tanks. Long story short i got an ich outbreak and put him and his tank mates into QT and copperpower treatment for about 30 days then kept them in QT for 70 with lower levels of copper. Every since we got this tuskfish it seems like his ability to see was off. He would rush food then back off at the ladt second, or miss getting it. He would be very picky and miss grabbing food constantly.

After the ich treatment and QT I have him back in our now 100% ich free tank but it seems he may be now fully blind besides some ability to see when the lights are on or not.

I've read this can be from the copper. Currently I have him isolated in a 10 gallon qt with no copper and have been treating with erythromycin and kanaplex. I dont think he has an infection but this is just incase.

I've been feeding him with tongs and poking the food in his face until he bites at it. That is working so far but he seems 100% incapable of finding food on his own.

The display tank is much bigger (100g) and I am worried he will starve to death as he is very good at avoiding tong feeding in the big tank.

I dont want to euthanize him but I also dont think this will get better and if I move him back to the display tank I fear he will starve to death. I need to be able to corner him to get him to eat from the tongs and this is impossible in the big tank.

Any advice? Any chance his sight might return?