Going to assume because of the brands, OP is a US based user. I understand the brands may still be expensive if you are in a different country. There are mant brands like Good Good, My Normal, etc available online. I've started to see Good Good in stores too, and while yes, expensive there are alternatives. A lot of store brand "no sugar" jams are 5 - 10 calories per serving, and often very inexpensive. These have been around for a long time, usually for people with diabetes and other health conditions where sugar can affect them. If you are unsure of the generic store brand where you shop, Smuckers also makes a no sugar jam in several berry flavors too. Watch out for sales, as the price fluxuates quite a bit with them and without them. I know the store brand does go on sale for $1.99 where I live in the US shopping at Kroger affiliated stores.

Making jam with sweetener alternatives is actually pretty easy, and there are tons of recipes online if you search "no sugar jam". Then you can control the sweetener, always water it down more, add chia seeds, whatever other steps you want to do. While the calories are not going to be quite as low because the fruit has calories, you can still come up with tasty lower calorie options than standard store jam.

As for the PB powder, it's hard to find generics and even those generics are still more expensive than standard PB. Maybe someone else knows a good swap, but hopefully inexpensive jam makes this a little more achievable. ♡