The charm of N900 as IM device disappeared many years ago. Sell the N900 to someone who needs it for its real charm

And yes, quitting Facebook is perfectly doable, and studies (biased?) indicate it may actually be your wisest move.

That said, the problem is not temporary. Facebook long ago said by April 2015, they would stop the xmpp service. We were on grace period all this time.

To develop alternative ... well