I have trouble accessing my Mac
What Mac are you using (Macbook Air / Pro)? Does it have a replaceable disk?

If the disk is not replaceable, I see the following options:


Assuming the T key is still functional: Access your Mac in target mode and unlock the disk from the other computer. For example this article explains the procedure.
Assuming the cmd and R keys are still functional: Recovery Mode
Assuming the alt key is still functional: Same as above, but you manually select the recovery partition


Sometimes the filevault2 volume cannot be opened easily. See here for a workaround.

If the disk is replaceable I would remove it asap, unlock the disk, and save the data e.g. with an USB-IDE adapter (like this one).