I was having a similar problem with another game, and I had a similar desire to learn general troubleshooting rather than have someone give me a specific fix. That said, I don’t know if I can help because for me it’s basically butt my head against a wall until I poke something enough that it works - usually I don’t know enough to understand why the thing works.

I was installing my games onto a secondary drive. The problem turned out to be that that drive had been formatted by Windows back when my computer was set up to dual-boot. Some games still ran fine in Linux, but this particular game nothing would happen when I clicked Play. On a whim I tried installing it on the primary drive with the OS, and it worked first time. So there was something about that game that didn’t work with the drive formatting.

(I’ve since reformatted the second hard drive so that everything should now play nice with Linux, now that I no longer have Windows. Game is fine now.)

I’ve never had a scarecrow wrecked. Can that actually happen?

The training rod is definitely not a new addition. I used it in my first game a couple of years ago because I found fishing too hard. There was a dialogue where Willy asked me how I was finding the fishing, and one of my options to reply was “it’s too hard”. Then he told me to buy the training rod. I don’t know if it was available before that; I never looked. But try talking to Willy when you see him and maybe it will come up?

The lake outside the mine is a good place to start. You get carp there, and sometimes they never leave the position your bar starts in, so you don’t even have to do anything to catch them - free XP!