You've contradicting your own statement. You said he is "not eating" then you said "not doing anything else for 20mins" and then said " eating smaller size than normal".
So what is "Anything Else" ? Is he eating or not? If he ate who cares how long it takes. Snakes have all kinds of behaviors different than humans or Animals because they are reptiles. The less you question why your snakes doing things the less confused you'll be.
If your snake slows its eating down you'll need to slow down feeding. This will happen sooner or later so before you ask whats wrong with him know thats what happens. You'll need to feed every other week at some point and as a Male expect him to fast for 8-12 weeks and thats just the way they are.
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