@korinathekoala
Heya!
You can mainly get pumpkin seeds from hoards (you can increase the chance using a seed potion brewed in the potion brewing station), interacting with other people (egg hatching ones I think are the best for the seeds). You can also buy them from market/usershop.

It depends what items? At least I think for pumpkins it hasn’t changed too much, plant products some like lucid have gotten more expensive I believe.

For the last 2 questions, yea! There’s pixpet adventure and pixpals to collect now which makes it really cool!