Hi there, I've adopted birds and it has taken YEARS to establish trust with some. I think providing good food, enrichment, and placing your "feelings" aside is the best way to start. You may never have the dream parrot relationship but you can provide a good life for this being, probably better than most. If you can get a bigger cage and can safely let Sonic out frequently, you will both be happier. Don't expect too much other than health and no vicious attacks and in the end I am sure you will be rewarded with much much more. Give it time and always be gentle, birds are incredibly smart and can almost always learn new behaviors with love, gentleness, patience, and time. Always approach your animal as if they are brilliant, wonderful and with trust and love, and you will be more likely to get that back from them. Be wise though, and don't put yourself or your animals in situations where fear, aggression, or anger is a likely outcome or you will likely get an unhappy result. As always, consider the safety and health of all your birds and family in this matter. If you find that rehoming is the best option for any of you, do it. Please try hard though to find a home and not a shelter. Think of it as part of your donation to the welfare of animals.
I wish you the best.
Cris