1. Yes, this is OK as long as the bird isnt spending all day or all night at the bottom of the cage. Constant sitting at the bottom of the cage is a sign of illness and should be addressed accordingly. My conure sometimes wanders around the bottom of the cage but lately has been sleeping on the sides or on a perch, it changes nearly every night. He sleeps wherever he is comfortable. I know he is healthy so the napping on the bottom of the cage doesnt concern me too much. You said too that he tries to watch the television through the bottom of the cage so I also think hes not down there because he's sick, more because hes comfortable or trying to watch the world around him.
2. He is regurgitating on you, which means he views you as his mate and loves you! This is great news because that means he trusts you and is bonded to you and sees you as his family. I know it can be kind of gross to be puked on, LOL, but consider it a compliment
3. My little ones nibbled for a little but I got him to stop by gently holding his beak and saying "no bite". I am not too sure about amazon behavior or if they are prone to nibbling and biting, I know someone else can chime in about that aspect of amazons.
Congrats on your birdie love - sounds like all is going well! Im so glad to hear you gave this bird a forever home, 3 owners already is a lot for a 2.5 year old, good for you showing him some love & stablity