Thank you very much for your feedback! I really appreciate it.
In case you still want to get that third ending, I can suggest that two of the three endings consist of you losing in different ways. One of these ways can be achieved without stealing a single thing, but still "losing the game". That (probably) should get you the third ending you were looking for.
And on your note about the monster speed:
The monsters speed scales with how many items you steal. So the more unnecessary items you get (not on the list), the faster it will get. At the very end it gets a larger speed boost, but still out-runnabe. Also, the monster can only see you if you are either withing it's sight, or you just collected an item. Then it will go to where it last saw or heard you.
The shopping list always stays the same as you said, and I thought that randomly generating the items positions would be enough, but yes, having a different list every time would have been more interesting.
Again, I thank you very much for writing such an extensive review of the game, it is really helpful :)