Advice on selling models?

Your main files are Blender, so you are in the lowest sector of professionals who purchase. Check the most common file formats for request. You should be saving the customers time, landscapes can be automated with many plugins. Scatters for landscapes are a better source, think grass/rocks/stones etc. Your backgrounds are mostly on black, switch to white. I see no cohesiveness, lots of random things which you mention you want to cater to but obviously its not working, focus on something then expand once you have experience.

I don't see any reason to start anything with Max or Cinema in this case, considering both skill level and cost of this software.
Improve your skills in Blender. Later also with Substance or Marmoset.

On top of what's already said by colleagues, very basic, bland and generic models, unappealing previews, non-informative description, ridiculous licensing, pricing on the high side for apparent quality, low number of models and overall views. Those are the main reasons of poor performance of your models IMO.

Too many questions - too little experience and skills. It's clear that you want to earn some money as fast as possible but only cats are born so fast. Go to Blender Guru YouTube channel (as one of the options) and take all tutorials. After that come back.

Well, your answer "I have actually already watched, I will look around" gives every reason to believe that there will be no progress.

And regarding prices https://www.artstation.com/marketplace/p/gMwWq/low-poly-isometric-kitchen-blender and https://www.cgtrader.com/3d-models/household/household-tools/rusty-pitchfork. I don't know what else needs to be explained here.