Bipolar isn't a death sentence - you can in fact learn to remain relatively stable and under control through the help of meds and behaviour changes (therapy can help).

As to the other... there may be a HIGH chance, but it's not 100%. Being prepared is good, but talking about having an expiration date? You don't know what the date is, so don't try to treat it like it's tomorrow.

It's his choice if he wants to have a relationship with you. I know that the urge to test someone to see if they're genuine, and to push them away if they are or don't seem to be.... I know that it's tempting when you feel so horrible about yourself.

But don't impose your thoughts and fears as being his thoughts - they're yours. He'll leave if he wants to. Might that happen down the road? Yes, it might. But you don't know that 100% just like you don't know that the Glioblastoma will come back.

He isn't staying with you because he's too nice. When he met you he already knew about what had been going on, and that didn't scare him away. He's not doing it to just be too nice - it would have been very easy for him to just not get involved with you because he had no commitment or feeling of obligation. He got involved with you because he wanted to.