it does not matter what size the cage is, the conditions are what is important.
Most longtime varanid keepers start out new monitors is very controlled conditions, which means, small cages.
The key is hydration, or better yet, lack of dehydration. A decent choice, and plenty of security.
What bothers me is the the reasons you picked that individual. A calm monitor is none pooping monitor is not the way you choose one. You want one that is feeding, so it will crap all over you. You want one with strenght, so it should squirm and even bite the crap out of you.
Becoming tame and trustworthy is what you will do after you have a healthy monitor. Now before. Its a bond between you and the monitor.
Also farm raised is total bullshat. PERIOD, I don't care if a monitor was hatched in my lap, thats again not the problem. The actual problem is what happened between that time and when it got to you.
Heres the actual problem, your monitor was either hatched for eggs collected in nature or from gravid females caught in nature.
The eggs were hatched and the neonates were housed in pens of hundreds to thousands, they were then shipped is bags full of babies, some alive, some dead, full of barf and [bleep]. They were then transfered from an importer, to a wholesales facility, again in pens of thousands, then send to jobbers, not thousands here, just poor conditions. Then to the person who sold it to you.
That person would not benefit from telling you the truth, there job is to sell product. Most do not know or care what the truth is, if they did, they would have to quit their job.
All you can do now is set up the monitor in proper conditions. Make sure is hydrated. As dehydration is the key to poor feeding response. Hopefully your monitor has functioning parts, many do not, liver and kidney damage from the above stress and over treatment.
So next time, pick one that has spunk and vigor, and worry about taming it later. At least you may have a chance to tame it. Sorry for the rant, but we have seen this to many times.
Your an victum of the system. So do not get mad. And its not the size of the cage thats important, not at this point. Set it up right, then respond to those results.
Remember, you have a reptile, it cannot support its own metabolism, as a reptile, it has to pick its conditions from its enviornment, or cage. if its not in the cage, it is dead. Cheers