First of all, you should not open all of those ports. Rarely will you need more than 5-10 ports. Change the ports in mIRC and set the same ports up in your firewall and router. Second, ports that are not in use may be listed as closed. Forwarding ports just allows access to those ports. The ports won't be in-use until they are actually being used.
As to your issue, it may be that your ISP is throttling your sends. That is not unusual in many countries and even in the US with some ISPs. Especially with faster internet connections. Sometimes the throttling is only on specific ports that they believe are the most commonly used for illegal file sharing. If you changed the ports to something else, you might not have the issue. Of course, they may throttle all large sends or there may be some other problem.
It may also be some issue with your router settings and it's hard to help you there without knowing the router and what you did with the settings. If you mention the router brand and model number, someone here may have used it and may be able to help more specifically.
And, just so that you know, you don't need a static IP to send files. There are specific reasons to set that up, such as having multiple computers on your network and you want to keep the forwarded ports on the right computer. But it isn't an actual requirement for sending anything.
