What was Paul's physical ailment which acted as Satans Messenger...

No one knows what Paul's condition was. Because Scripture doesn't tell us, we cannot know. People have thought it could have been an eyesight problem, or it could have been pride. The fact is, that whatever the problem, it didn't prevent Paul from serving his Lord wholeheartedly. Paul suffered many privations. He was beaten many times and suffered all sorts of problems. In all things, he was sustained.

Bible scholars believed that it was a crippling ailment in order for him to suspend his 'fullblast operation' of spreading the Good News.

I think what he was actually talking about is either his pride because as it discusses with Satan kept pushing him down or the other view point of it would be like the good angel / bad angel on your shoulder. Kind of like in the cartoons where because Paul was a virgin his entire life that would cause him to have thoughts of woman that he knew he shouldn't have and then the "bad angel" or devil as he calls it would come out and tempt him.

its some eye problem which he quotes to some church saying that they were ready to give their eye for him