Thanks for taking to the to write this feedback!
1. Good suggestion, i'll add a display showing item sets better and before you get them rather than latter, probably on item hover. Also include more item sets.
2. Another good suggestion, will look to implement but down the line.
3. Will be adding this too
4. 1,3,9,27,81 makes sense. I'll implement that too!!
Thanks again for the feedback, very impactful, at the moment i'm in the middle of implementing a new progression system, so this feedback will be incorporated between that patch and a few more afterwards.