Sending 1 out of N doesn't seem quite right.  I think you want to 
send at most N per second.  Am I missing something?

I'm thinking of something like this:  Don't send if a counter is 
too high.  Bump the counter up by 1 when you send an error packet.   
Bump it down by X % every Y milliseconds.  If you scale by 1000 or 
1024 you can do it all with integer arithmetic.