"She actually snogged the Teselecta Robot disguised as the Doctor, with a miniature Doctor inside. To which you could reply
it didn't have to be physical contact, just close enough..."
Ah no. The fixed point was that River would kill a robot that everybody thought was the Doctor. So she had to come into contact with the robot.
The Doctor figured that out. He knew the fixed point had to be River killing something or somebody who looked just like the Doctor, because he'd seen it. It din't have to be the Doctor himself. Most Whovians had figured that out, but the most common prediction was that the Doctor on the beach would be a flesh avatar.
"While it was unfolding it had the possibility to be rather clever but when you put everything in order it at the end it's on the wrong side of the 'a little bit too silly' line."
You've got an alien who looks completelt human and can regenerate when the plot, the actors career or the BBC's internal politics require it. He can travel in time and space in a little blue box which is an awful lot bigger on the inside. He can fix almost anything in the world (except wood) with his sonic screwdriver, but can't fix the chameleon circuit of his TARDIS. Time can be rewritten. He can't travel back into his own personal timeline, except when he does. Etc. Etc. Etc.
I'm sorry but I think you'll find that almost any Doctor Who plot is well over that line. But there's nothing wrong with silly.