No, there is no option to make the max window float. I suppose you do know that ctrl+m will always bring it to the front though?
Also, if you click on the Max 5 icon in the system tray it will bring all max windows to the front. After that ctrl+m will bring the max window up if it is not already.
Or, right click on the Max 5 icon in the system tray will give you a little menu that lets you show the max window.
To change the font size of the max window you can use the font panel which is brought up by the Object -> Show Fonts menu command (ctrl+T shortcut). Just open the font panel, bring the max window to the front, and then adjust the font. Whatever you change it to should be remembered for the next launch.