Keep it in for as long as there's a large krausen (the foam on top of the beer.) You can then choose to remove it and replace with an airlock or you can leave in until the end of fermentation and you're ready to rack. If you do remove it and replace with an airlock, there is potentially a risk of contamination, but not much if you sanitize all the airlock ...
You essentially have four options:
1) Use a blow off tube.
Advantage: Easy to do.
Disadvantage: You risk losing some beer.
2) Find a bigger vessel.
Advantage: No beer lost.
Disadvantage: You need to find a bigger vessel.
3) Use a foam suppressor like Fermcap.
Advantage: You'll lose less beer than with a blowoff.
Disadvantage: Some people don't like ...
No worries. This is exactly the point of a blow-off tube: to blow-off excess fermentation products (krausen and wort trapped in the bubbles) in a controlled, "sanitary" way. There's basically no contamination risk. Swap out the contents of the blowoff container if it gets too nasty, starts attracting fruit flies, &c. But leave the blow-off tube in place ...
A lot of brewers use silicone tubing for hot liquids, but there's no reason aside from cost not to use it for racking as well. That will take if the tubing part but you've still got to deal with the racking cane which is rigid. Copper or stainless tubing could be bent into the correct shape.
That's a question that's been debated with no definitive answer. Some say it's better to blow off the braun hefe becasue of the bitterness it might contribute. Others say it's better to use a larger fermenter so you don't lose yeast. There really is no right or wrong answer other than "try it each way and decide for yourself".
If vinyl isn’t the gold standard for homebrewer’s tubing, I don’t know what is. It’s good to ~170° F max.
As Tobias mentioned, silicone tubing is used for higher temp transfers.
Purchase anything anywhere “Food Grade” and you’re good-to-go for low-temp homebrew, but I wouldn’t get too creative with random hardware store DIY bric-a-brac without the “Food ...