Hello, and welcome to the forum!
It depends how big the bowl is. It kind of also depends what the decoration is, too. Bettas need a place to hide. How big is the bowl if you know and what is the decoration? I do not think that is enough. My opinion is the smallest tank for a betta would be 2.5 gallons. Some would say 1 gallon, but it's up to you. 1/2 gallons are definitely NOT good though. Bettas enjoy live plants and caves to hide in.
A bubblenest is basically just a collection a bubbles a betta blows. They blow a bubblenest when they're comfortable in their surroundings and are ready to spawn, if I understand correctly. Here is an example. They build their bubblenests into layers as well. This one is flat.
I would say a bloodworm once or twice a week would be sufficient, but I don't feed them bloodworms that often. Other members can help you with that.
I do know that you should feed two to four pellets a day, so maybe two in the morning and two at night.
Hope this helped!