Question

What happens if you have Param 1 in your ad, but there is no corresponding value at the keyword level?

Answer 1

well, that's an interesting question to ask.
If we will only have 1 param without any corresponding value at the keyword level then in the result that ad will not serve , Also in this case the ad will exceeds it's character limit. . 
Additionally if there is no corresponding it will also  result in non functioning of destination URL.
Another important thing is that if that happen then even the title will not appear.