Indoor lemon husbandry

I have a Meyer lemon tree in a pot. I’ve had it for a little over two years. Its first season, it didn’t flower. I changed its feeding and light. Its second season it flowered, but did not fruit. I upgraded my pest-management regime. The third season it fruited beyond my wildest dreams. So far so good. Now, at the end of its fruit season (I didn’t count, darn it, but I bet I got a couple dozen large lemons off of it), it appears to be dying. It’s turning black and brittle from its extremities inward.

Should I prune deadness and repot in new soil? Should I bleach the roots in transfer? Should I bathe them in a baking soda solution? Should I leave well enough alone and pray? Should I have fed it more while it was producing those massive amounts of tart yellow matter?

Any clues or hints will be greatly appreciated.

I think that you should trim off everything that is dead for sure, even if it is half of the plant. My experience with plants is limited, but I’ve hacked down some sickly plants that have made astonishing recoveries.