Orthodontics by itself cannot assist adult patient's with skeletal discrepancies of this type. It can assist patients when treatment is combined with maxillofacial surgery.
Your teeth are definitely protruding. It seems that you were quite crowded before orthodontic treatment and you might have needed extractions to align the teeth and reduce the overjet. If you want to avoid extractions then you have to accept the current teeth position. Discuss the matter with your orthodontist, I am sure he can offer you further treatment if required.
Retainer is supposed to have a real tight fit otherwise your teeth could relapse. They are made in a laboratory using special materials. I would avoid the self made retainer since it could allow unwanted tooth movement
No gaps will appear after orthodontic treatment if you use your retainer as prescribed. Retainers help keep the teeth straight and avoid relapse or spaces opening up. A fixed retainer could be an option in your case
Yes we can bond brackets on artificial surfaces, including composite fillings. We have to use special bonding agents in these cases
