I'm not sure how you get to the main menu, but usually it's by pressing ESC after you load the game.
Oldbroad's suggestion was a good one. In that manual does it explain the main menu functions? It probably won't mention navigation as such, but more what things you can change in the Options sub-menu.
If the numbers above don't work, that tells me the numbers on the keypad shouldn't work either. Maybe try turning OFF the number lock so they can't be used as numbers? You don't say so, but I assume when you tried to use the WASD keys, they didn't work?
I hate that, Tally Ho! Big Fish drives me crazy sometimes! And then it just repeats over and over. And you have to turn the sound up. And you have to go to YouTube if you want full screen. AND, if you go to YouTube while it is playing on Big Fish, it continues on Big Fish and you hear it from both places.