If it were me (having grown it from seed and looked after it for 20 odd years), I'd most definitely give it a further year in the ground, before making a final decision on removing it (fingers-crossed it won't come to that).

In the meantime I would:

* Spread a 50mm layer of good quality compost all the way around it (about 1 to 1.5m diameter). This will feed the tree naturally and slowly.
* Keep a regularly eye on it & check for any sign of pest damage/infection.
* In warm, dry spells, make sure it gets a good drink (water slowly & deeply).