You don't need a tour card to turn pro. He simply earned his after he turned pro.
A tour pro keeps his card if he places in the top 125 money-winners on the PGA Tour
Tiger Woods joined the PGA Tour in 1996.
A tour pro keeps his card if he places in the top 125 money-winners on the PGA Tour
His first full season on the PGA Tour was 1997.
A PGA Tour player, can use any golf ball that is on the list of conforming golf balls, which is published by the USGA and R and A. The PGA Tour operates a one ball rule, this means if the player tees off with a Pro V 1 x on the first hole, the only ball they can use during the tournament is a Pro V 1 x, or they will be disqualified.
Yes, and they are very popular. You will rarely find a PGA Tour pro who doesn't use one. On the Champion's Tour and LPGA/LET Tour they are extremely popular, with players having at least one, but some players carry as many as 3.
by looking on eBay and Amazon, the average for the set is about $10
Yes, they do. A major championship win carries a 5 year exemption on the PGA Tour, and the player may accept this. However, due to the huge amounts of money earned on the PGA Tour they will most likely turn pro, as amateurs can not collect winnings.
X Stiff would be standard for a PGA Tour player.
I think you are combining two concepts. You can join the PGA by being a professional in the golf community. This can be a playing pro, teaching pro, club pro, etc. The PGA has a long list of types of pros and PGA members. A "Tour Card", what you typically here about for Q school, or "keeping their card" is a level of exemption for playing on the PGA Tour. Not all PGA professionals are qualified to play on Tour (in fact, most aren't). To keep your card, a big requirement is to place in the top 150 on the money list (I think). You can earn your tour card by placing high enough in Q School, top 25 on the Nationwide money list, etc. You can get exemptions into tournaments based on your play, too. It's complicated to cover all the ways to get to play on tour. I think if you win the Masters, you get an exemption to play in it for the next 10 years as one example. You can play as a pro without joining the PGA. You just declare "pro" in an open tournament. Go out on Monday and qualify. Make it to Thursday. make the cut. Make some money!
There is no minimum they have to play because they could get injured or something.