Many bowlers bowl with spans that are too long. The symptoms are often what you described a “burning of the finger tips” or even blood blisters. If you don’t bowl a lot this will not really be a problem but if you start bowling more then it becomes an issue.

Almost all the pro’s on the tour use a relaxed finger tip span. This allows the most versatility in releases and puts the least amount of wear and tear on the hand.

You should be able to put you thumb fully into the ball and then lay (don’t stretch) the palm of your hand on the ball and let the fingers lay on top of the finger holes. The first knuckle should be at least 1/3 the way across the hole/insert. A little shorter is ok but not longer.

As far as flexibility of the fingers go. You can become less flexible over time particulary when like you quit bowling for a while. Not stretching the span will help this. But as Ragnar said you can pitch the fingers away to help this. Generally the proper span will allow you to use zero forward/reverse on the fingers.  

I may not have said it well. A little shorter span than 1/3 the way across is ok, in other words 1/3 the way across is the least amount your knuckle should go across the hole. So your 1/2 is fine. But longer spans often do hurt their user.

Stider, Funny, I thought the same thing.  That just shows how easy the left side is.  My good looks and natural talent will only take me so far, now I'm ready to learn to bowl.