You do not want to "power feed"!
There is no reason to feed a snake more than twice a week.
If you feed twice a week offer smaller meals.

If you feed once a week then offer appropriate sized meals, usually the rule of thumb is 10% of the snakes weight should be the weight of the prey. Or visually a prey item that matches the width of the widest part of your snake.

It will just take time. After a consistant feeding schedule then the snake will gain weight. I would suggest buying a digital scale that measures grams. Keep track of his weight once a month and see how it goes.