welcome to the 360 lovers corner
I have an old 360, but have tried to adapt the themes of the 360 for my 903, and it can be done: there is a compiler for the themes, so you can easily modify an existing theme to redericet the applications shortcut to the correct folder - if you have a go at the (long!) themes thread to try and get an idea, then if you want to try and mess about we can talk about this more.
As for the readers: you do not have to substitute, you can add fbreade180 and coolreader. The advantages of the two latter reading software is that they are also very customizable - coolreader in particular keeps a lot of the book formatting (including scaling of pictures as far as I can remembert), so you may want to have a look. Above all (for me!) these two readers allow you to turn pages just by turning your wrist - so you can forget about the buttons, which is great if you are reading on the beach with your reader tucked into a ziplock bag, or if you are standing on the underground and holding with the other hand to a railing, or in a host of other occasions.
Can't help you with the browser (your firmware is probably similar to the pro models, but I have a touch device, and I think the browsers are different between the touch and non-touch models).