You can change the text size in the browser using control (or command on a mac) and the + (really =) sign for larger or the - sign for smaller. those two keys are the ones next to the backspace key and NOT the ones on the Number Pad if you have one.
Please note that it will affect all text in the browser, so, once you are done, using ctrl (or cmd) and the number 0 will reset it to the default text size.
Another, less pleasant and significantly more time consuming, option would be to edit the HTML of the game and change all fount size references in the actual game code. I only list this for the sake of completeness.
Edit: For starting a new game, normally there'd be a button on the left hand side bar that would let you start over, but that does not appear to be the case here. You could potentially clear your internet cache, but I haven't tested that to see if it works. You can move the HTML file of the game to a new folder, and that should also let you start a new game, renaming the folder the HTML file is in i think might also work.
However there does not appear to be a way to start a new game from within the game.