Depends. It depends on how much and how many tubes.
No you will not die. No you will not die. However it is ot intended to be swallowed but if small amounts are swallowed there will be no harm.
Nausea. Nausea is likely, but it depends on the amount for more severe reactions.
No. Toothpaste is just soap, sand and a little sweetener. I you swallow just a small amount while brushing it will have no effect. You would become sick long before you ingested enough to do any damage. We're talking tubes, cases of tubes. At this point it wouldn't be accidental.
No. It will make you sick to the stomach before you reach toxic levels. Kids, however, can harm their still developing permanent teeth if they routinely swallow even small amounts of tooth paste over a period of time.
Only. Only if you swallowed bathtubs full each day. You would have to consume huge amounts for it to be fatal. You swallow tap water all the time. It's chlorinated to help prevent Typhoid, yet chlorine is toxic if huge amounts are ingested. Swallowing a little bit of toothpaste, like swallowing a little bit of water, is not going to hurt you.