Sue, I agree with your conclusions.
The first number #3 was probably the original cause, and the second #3 is the best course to take(given Killian's physical state given by your Vet's evaluation).
Sue.. I know that you are very 'in tune'
with your babies and will instinctively choose what you feel is the best course to take. You have my complete support and continued prayers. All the best. Liz