Craig, I am sorry you have this limitation put on your singing. But have some perspective, it may help you persevere.   

For example, I'm sure you don't sing in the Peggy Lee style, but she had a very long and good career, yet her useful vocal range was actually less than an octave.   Another example is the scurfy-voiced Bob Dylan, it never slowed him down not having pretty pipes.   There are countless other singers who have done fine with very imperfect instruments.

You may have to get very nimble at transposing things into 'your' key rather than singing any song in any key. This is a burden but also an opportunity to boost your musicianship. And you might sing more to convey the lyrics in a heartfelt way rather than to sing out great notes like a great flute or horn. But many of the best singers do that. The singers I dislike the most are the 'note-worshippers' who are simply stringing together vocal acrobatics for their own glorification rather than telling the story of the song for the hearer.

I know these remarks are probably not too welcome right now when you just want to 'fix it' as much as you can. But if you can still sing at all, and people still want to hear you, do not let technical problems hold you back.

And do get a vocal coach, teacher, or even choirmaster who can help you carry on without doing further damage. Singing 'right' can help you stay healthy and make the most of what you have without further damage.