Force feeding.......

I have Tilapia Mariae that has been in my care now for nearly 11 years he is in a 60gal tank on his own, he has been healthy all that time, until now....I noticed around 2 years ago some erosion/loss of scales around the sensory pit areas on his head....fearing HITH I initially doubled his w/c regimmine to twice weekly 25%, and the 'holes' never worsened after that. Around 5 weeks ago he became a little more fussy in his eating he stopped eating his usual pellets an would only eat bloodworm...I don't like feeding too much bloodworm as from experience I know it causes constipation....and the he stopped eating altogether....I initially tried Epsom salt at 1 teaspoon per 10gal..and he produced normal faeces....but still refused pellets I thought he was being stubborn and holding out for bworm so I'm still not too concerned...but the days went to a week without food and I became increasingly worried...I started a course of Octozin(this is the only UK med with Met in it), I treated a half dose as I thought the meds would be very effective as he had never had them before, sure enough after the 3 days he ate as normal. This was the last time he has eaten....that is now over 4 weeks without food. I waited another 3 days the did a big w/c and noticed what I was dreading thread white and clear faeces, the second course I upped the dose to three quarters recommended....nothing, again waited till day 6 before w/c and recommenced treatment this time at the recommended dose....instead of treating 3 days then backing off I continued the treatment at a lowered dose for another 3 days and went back up to full dose I am now at day 9 of treatment my reasoning was that if I am killy some of the parasites and not all surely if I back off they will just replicate and build their number up again putting me back at square 1.
So now I'm at my wits end...he is still ignoring food, I have added Epsom again. I read an article on this forum about force feeding with Epsom soaked food, it basically said that if you can get Epsom into the gut it kills the spironucleus parasite very effectively...so I have ordered a pet medicine syringe and think if he dosen't eat by this sunday I will do a very large water change and back off the meds and try force feeding, I'm terrified though that the stress of netting him and shoving a syringe down his gullet might prove too much...plus I'm scared of hurting him trying to hold him to get the food in....I know it could save his life though. Is there anything else I can try bearing UK meds in mind.... I have ordered a pack of worming meds ....it is recommended for discus so I know it wont be too harsh.. I was going to try this after a few days and waterchanges....any tips on the feeding or other thoughts welcome....

The wormer med is called 'Kusuri' it uses Flubendazole as its active ingredient..meant to add the fish is remarkably not too emaciated after 4 weeks and still stays in his usual position in the middle of the tank, not sitting on the bottom

Believe me RD I've thought of little else over the past month.....when I got him he was around 3 inches so I'm guessing he must be around 12 or so. But the signs all point to some kind of 'Hexamitta' parasite, the initial erosion now the clear mucous faeces and I know that is curable.....still annoyed with myself for giving him bloodworm and constipating him. Do you think its worth trying the force feeding with food /Epsom as per your sticky or would you just back off ?