Ok. You'll want to hold off on handling til he gets eating consistently.
Medium rats are also too large. Most males never need anything larger than a small rat, definitely not at a year and a half old.
Larger prey items often lead to refusals and food strikes.
I have two adult males around 1,400 grams each. They eat a small rat every 14 days or so. They pretty much never refuse a meal. I've gotten to the point that I basically let them "tell" me they're ready to eat by reading their body language.
Also, it's possible the prey isn't getting warm enough. Are you using a temp gun to check the prey? It might be worth it til you get the hang of feeding. You want the prey to be wround 100°.