If you aren't going to listen to reason, then there is no point in anybody continuing to waste their time responding to you.
As everyone else here has already stated more than once, this is not a port forwarding problem, and unless you are doing something super-duper strange in your RouterOS config that you are not telling us about, it is with 99.999% certainty that I can say that this has nothing to do with your router. Virus definitions are PULLED by the antivirus software from the server, not PUSHED to each individual computer by the server. A push arrangement would never scale: antivirus software vendors do *not* maintain a complete list of every single active computer that has their software installed on it and then initiate mass-definition update pushes out to all of them whenever definitions get refreshed on their side.
Besides, if it was a port forwarding problem, what single host out of all the workstations on your network would you choose to forward the port(s) TO? You couldn't possibly solve every computer's problem this way; you'd have to limit yourself to one. Which is ridiculous and doesn't make sense. Also, opening up specific ports for unsolicited connections from outside your NAT+firewall to every host on your LAN 24/7/365 is a security no-no. No software vendor would require you to "open ports" to pull down software updates, and certainly no AV vendor is going to require you to open up permanent holes at the head of your network to all hosts on it.
Use common sense, please. Dollars-to-donuts say that virtually all antivirus software vendors -- just like virtually any software vendor doing digital distribution today, period -- are serving up their updates from a web server, via HTTP. Do you need to "forward ports" to be able to browse specific web sites? No. No, you don't.
If you are still convinced after all of this that your problem has something to do with your router, then post a complete '/export compact' for the members of this board to comb over. But I'm telling you: you are looking in the wrong place. If you are so convinced it is a problem with your router, then replace it with something else for a day and see for yourself.