I read that there is an ED-E quest that utilizes Old Lady Gibson. Unfortunately, the Old Lady is permanently sleeping quietly along with her two dogs because I didn't want to give her the 500 caps to help sabotage Jason's wacko cult rocket ships. Anyway, I haven't even fixed ED-E yet, but have I ruined any chance of getting him as a companion because Gibson refused to accept a better offer?

no. there are multiple "triggers" for ED-E, Gibson is just an easy one.

You have to have ED-E as a companion already for the triggers to work. He has to be with you...in case you didn't know. The triggers allow the ED-E My Love quest to move forward for upgrading ED-E's weapons or armor.