1. and 2. - I'm level 50 with nothing but the Halcyon Rod, the Fisher's Gloves, and some level 40-49 HQ stuff I bought off the market and I've been able to catch every fish in the game save the Mushroom Crab, but that's only due to it never being foggy in the Black Shroud (Grr...). I recently managed to finally afford the Fisher's Wading Boots HQ, but I had already caught some of the toughest fish in the game (including Dinichthys) without them. If you have the full set of green Fisher gear (even if it's not HQ), you shouldn't have any trouble catching it unless it was an HQ one you were trying to reel in. Those are tougher to catch. Is it actually saying the fish got away when you try to catch it or are you simply assuming you can't catch it yet because you haven't seen it yet? It's a double mooch from the Wahoo, which is a mooch from the Merlthor Goby.