In general you want to put things like item statistics, level up experience point thresholds, and any other "pure data" into some kind of text file or database, and then read it into the memory on load or when you need it.
Look into exporting and importing JSON objects, and write 'types' in your code that are read in from JSON files. Then when the game or level loads, you read in all of the item statistics, for example.
Nice job! The presentation is very readable despite the inherently cluttered playspace of a TD game
I liked the original but found it a bit too punishing/affected by RNG. But I LOVE the sequel - they smoothed out the worst rough edges and made things more predictable. For example, no more hit% for attacks - now attacks hit unless enemies have a Dodge token, which gives then 50% miss chance and is expended after one attack against them. And of course the roguelike structure is a great fit. I feel like this is the perfected version of Darkest Dungeon mechanics - you will suffer, odds are overwhelming, but you have a lot of options to mitigate or occasionally even benefit from bad status effects, and combat is much more predictable.
I think it's a great game and I'm interested in the DLC.
Yes, try to find a different job. It's tough out there right now, as you probably know, so don't quit until you've secured a position at a less crazy place.