Vent tube question 68 Barracuda

I've always had to fill my tank slowly to avoid continual splashing back of the gasoline every gallon or less. And it's a pain to get get it full. I was told by someone it could be a clogged vent tube. I removed mine and found the top end had the flared bulb with a smaller hole than the tube.

Question 1) should air flow through the tube when I blow compressed air through it?
Question 2) Is there a check valve of some sort in the end?
Question 3? what would happen if I cut off the end so the opening is the size of the tube?

Thanks!