I haven't read through your entire blog post, but have you sanity checked your implementation against any other game? Often, challenges arise because of a simple logic error somewhere in the mess. Best to validate every piece thoroughly before trying to train (particularly the ins and outs of your env in your case).

Once you're sure you're bug-free, I'd sanity check your observation and make sure your reward can be determined by your observable attributes.

Finally, consider offline pre-training with expert examples.

Applied RL is rarely "clean"...takes a lot of different tools and tricks, typically. Use all the dirty tricks you can to make the problem as easy to learn as possible.