Even if your mouse isn't working Windows is navigable through the keyboard (although tedious), for OK button 'click' you can hit enter/return, to move around buttons to highlight them you can use tab, alt-tab to switch between windows or apps, alt to activate the menu bar, arrows to drive drop-down menus, cmd-key to bring up the Start menu, alt-fn-F4 to close the top window, etc.
Although you're trying to use Fusion, the time I checked you can't uninstall the Parallel Tools without their software. You may want to check for an update on this issue on Parallel's forum (it is their software after all...)
One thing you can do without uninstalling Parallels Tools is delete the mouse device (via the keyboard) and use plug-n-play to re-detect VMware's pointing device. You would run device manager (Start > Run > devmgmt.msc > OK), use tab to highlight the computer, then down arrow to get to "Mice and other pointing devices", use right arrow to open the section, down arrow to select the active mouse. If there is no mouse, use alt to bring up the menu bar and toggle View > Show hidden devices. Finally use fn-delete to delete all of the mice present, then use alt key to select Action > Scan for hardware (this is plug-n-play). After this you should have a working mouse, if not re-run (in OS X), Virtual Machine > Install Vmware Tools.
Yes working with devices is UGLY in Windows but it comes with the territory even under Fusion and OS X. Once the mouse is working, it should work going forward.
