OK, sorry, I missed the point and I may not be experienced enough.
But to try and be helpfull, there is a site called "easyfwgen"
that may help you configure the firewall (iptables), but you probably don't need that.
There is also a few sites that you can use to check, shields-up from www.GRC.com
(Gibson Research Corp.) but only checks the first 1500 ports, so most used.
this is a bit more complicated but offers a real perspective of what ports are accessible from the web.
I hope this helps.
Even if you run the easyfwgen to get an idea, save you iptables file first, of course, but this may shine some light where we have missed.
Also, iptables is pretty secure (stealthy) with out user intervention.
See how you go, and I hope that an expert soon corrects me if I am wrong (outrageously)
I'm pretty sure it is good as you have it, but I hope I have given you a few ways to check.