I didn't think of that. The alchemical tome is one of the things I took a look at in a regular survival game and decided was an expensive waste of time I think it's a pity you can't make uranium from UU-matter any more. I quite like the idea of having to make your first UU-matter without nuclear power before getting a reactor.
I suppose chopping a tree would be faster. The fishing idea came from me wondering what I was going to eat. The only alternative at the start is apples, and you start with a piece of string, so I gave it a try.
It's worth lighting your portal with a flint and steel because it's much faster than messing around with lava and you can burn it in your transmutation table afterward.
By the way, there are a lot of items you could either leave out or move to the Nether to make the map harder. You can get string from spiders and leather from cows once you get them. The gravel, sugar cane, clay and cactus can be moved to the Nether. The Nether chest can contain no mob eggs and just a single ordinary egg. Throw eggs to get chickens and use your philosopher's stone to transmute chickens into other mobs.