Thank you for the comment! It's great to hear you enjoyed the game and found it inspiring.
I must admit I haven't worked on or even looked at "The Tree" in a couple of years, so I had a difficult time answering your questions. Looking at the code, the Merchant has one unique dialogue option near the end (and gives you a small buff) if you spent a lot.
I agree the game is not perfectly polished or balanced, there are some bugs I sadly were never able to fix, some enemies may be too strong or too weak, and the RNG can ruin even good plans. It was a "speed project" for me (I worked on the initial release and each of the two big updates in bursts between writing another, bigger game, and I think I only spent 2-3 weeks total on it), but it was a good way for me to test out new ideas. If you think about learning Twine, I'd say go for it - it's great fun - and consider starting with something small. I also can't recommend the 'intfiction' forum enough - it's a super friendly community focused around text games and a good place to find beta testers, help with your code and general design, news about competitions you can enter to showcase your work, etc.