Giving them new food can be a challenge.. trust me I know lol.. I have a wide range of food from pellets, live, home made, flakes, freeze dried, and on and on. And I have some very picky eaters.. one of them will only eat pellets. May be because he's a couple years old and is just too stubborn.. and I have some that will eat anything that lands in the water.
You may want to try to play up his natural predator instinct with the worms- I like to use tweezers and grasp barely just one end and let the other end of the worm (or insect) barely dangle in the water- since the worms aren't live you will have to move it gently to it simulates a bug at the surface.
If he falls for it then you can have fun with it.. such as make him jump out of the water for it, or even learn to go through hoops lol. Just be warned, once he starts jumping for food, he may always try to do that when you go to feed him, regardless what you are feeding.
Also, that morning don't feed them (assuming you are properly feeding at least 2x a day).. make him a little hungry. Don't give him a pellet, just offer the worm and see how he does. I wouldn't put more in there if he isn't eating the one.. if you do, remove them shortly after attempting to feed so they won't decay in the tank and foul up the water.
Peas are not to be fed on a regular basis- the betta's short GI tracts and the fact they are insectivore/carnivores means the pea will do nothing for him but give him empty calories and carbs (the same they do for us). They should not be fed on a regular basis.. no nutritional value to them and not a treat as it's nothing like their natural food.
You can give live foods- place a bucket of water outside, toss in some leaves and a little bit of dirt and wait- daphnia will breed all year round, and mosquito will breed in the stagnant water. Just use a shrimp net or a small fish net to collect the larvae, rinse in gentle tap water and feed!
