I wish you would put the Betta in a 10g. He could probably go in the tank with the shrimp. Try it first with a few shrimp. He looks like a mild tempered Betta so I think it would work.
do you feel like the bowl is too small for him?
the 3 gallon has been a consideration but mixing him with the shrimp wont work due to the 50 babies im currently raising in there, unless i relocate the shrimp