Welcome to the Forum. You seem to have learned about the overall low risk of receipt of oral sex already so I'll go straight to your questions:
1 I know its a low risk event but what are the chance of me getting an STD i.e Gonorrhea with me taking 1g of zithromax 4 hours later. 1/100 1/1,000 1/10,000
There are simply too many variables to give you a firm estimate of your risk however I am confident it is far lower than 1 in 1000. The odds that your partner had oral gonorrhea is substantially less than 5% and if she was, the odds of her transmitting it to you are certainly less than 10%. IF you had acquired gonorrhea, the azithromycin would have cured over 70% of infections and any remaining infection would have been symptomatic. Putting all of these factor together, there is really little reason to worry or, for that matter, test further.
2 Is my wife at risk for an STD she was also on the second day of a zpack for a sinus infection when we had sex.
the presence of azithromycin in her system would have made her less likely than average to become infected. How much less has not been studied.
3 how long should I monitor for symptoms before I can put this behind me and assume i am in the clear, if i have no discharge or painful urination.
Symptoms or gonorrhea would have been obvious and apparent in less than a week.
4 Can i assume that painful urination would be unmistakable?
The symptoms of gonorrhea are typically obvious and it is clear that you have been looking for them.
Summary: Your risk of infection from this exposure is low and not something to worry about. I hope my comments will help you to accomplish that. EWH