Absolutely stunning! In my opinion, they really are the most attractive Monitor. It's a pity that they can be so temperamental and they get so large.

Feeding frequency depends on the animal and their age. At four years old, a few times a week is more than adequate. Younger animals often require daily feedings, but he looks like a healthy weight so you should just be maintaining that. Make sure he has proper basking temperatures to properly digest and give him exercise if you guys don't have a large enough cage yet.

Whole prey items are the way to go with Niles. Whole chicks, rodents, etc. should be his staple. Keep in mind that whole chicks are fine, but it makes for very stinky defecation.

FYI, in case you didn't know, these guys are VERY fast. Don't be deceived by his size. Also, what do you have his current basking temperatures at?