1) How do you know only Santa has seen flying reindeer? Also size does matter, perhaps this magical group has the ability to change it's size. Or transport ala Star Trek ( Roddenberry had to get his ideas from somewhere, perhaps he saw the flying reindeer as a child as they "poofed" out of nothingness and used that as his template).
2) Refer to the theory on transporting.
3) Again transporting( DUH! loud sigh ). Also every kid knows that Santa subscribes to the theory of wormhole travel. And as every kid knows when you travel via wormhole you "warp" time thusly creating vastly more usable time within the same moment.
4) Well I already told you about the wormholes, didn't I? He doesn't need to carry anything but an empty sack and his trusty handheld wormhole generator. He obviously just opens the wormhole to his shop, picks the toys that he needs for this particular home and carries them into the house in the sack.
5) We've already covered this "speed" thingy in the first 3 responses.
We must all remember that Santa is a magical being who was raised from a mere mortal man by the power of GOD (that's right I said it!) for his love of the needy children of his community and his great deeds for them. He was even sainted for this ( Saint Nicholas ), look it up. He was granted great magical powers as well as advanced knowledge so that he could keep up with the ever increasing numbers of children worldwide.
When he started out all he needed was his trusty sleigh and his mule, but as time passed he was able to change with the times. He chose reindeer because they are nicer to look at. Although the mule is still his oldest and dearest friend.
I could go on for hours but I believe that I have made my point very clearly,Santa does indeed exist!
Do you believe in GOD? Ufo's? Air? Have you ever seen any of them? Just because you can't or don't see something doesn't mean that it doesn't exist. Believe with your heart, not your head.
My answer took several thousand hours of pain staking research and took my staff to 79 different countries. Fortunately we were granted the use of Santa's transportation device and wormhole generator so we were able to finish everything in just 14 minutes. Oh crap, I've said too much!