I cut or just shave off only what you need for that feeding that way you never have any waist. Or you can take a couple of cubes cut them up into smaller portions and freeze in a ice tray with some water in each one, i use the small cube silicone ones from Walmart, cheap and they work.
If you can put him in another tank for a week or two and let him rebuild his strength, after you reintroduce him I would watch close, I have had the female kill the male after breeding and vice versa, you may need to relocate him to his own tank for awhile. Good luck
First thing is how many gl., is it a tank that is display or breeder? If it is a tank that is breeder, for the cheap but effective you could go to Lowes/Home Depot and just use a piece of 1" aluminum flat bar and just bend a 90 dig. angel on each end to hold the top where it is supposed to be or...
I've been playing with kribs for awhile and having more than one female in the tank has never done well for me. Like chromedome52 said break the line of sight and lots of plants and hiding places, and keep a close eye on the tank for aggression and have another tank ready. Good luck
He does not look all that fat to me but does look like a old boy, when there head gets bigger than there body I have heard that means there getting old, but to be honest my oldest apisto I got in 2017 all my others are younger than 2 years. Do you know how old he is?