Beautiful leo!!
As far as feeding him goes, I would not so much worry about how many you feed him. If he is hungry then by all means feed him. The size of crickets should be determined by the length from one side of his head to the other. So the space between the end of his mouth on the left to the right.
We only have 2 leos so the way i do it is get 5 or 6 and put them in the duster jar i have then just dump then in the cage a few at a time. This allows me to monitor how many he is eating and make sure that none of them get away or hide etc. If he eats all that i offer in a short amount of time i then go get him more. I do this for about 15 to 20 minutes and he either eats them all or he gets full and is done in which case i pull any uneaten crix out of his enclosure. He will usually eat 15 to 20 crix a feeding plus a few mealies or wax worms when they are offered then he is done. In other words feed him however many he will eat in a 15 minute period, I wouldnt judge from numbers.
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Mike & Wendy 
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