Speed problems with qbittorrent 4.5.1

[Twisted]

My connection is gigabit fiber. I tested that I am connectable, but I'm having the following issues problems with qbittorrent:

1. Upload is never more than 40KB/s (max set to 75MB/s)
2. Download speeds vary a lot. Sometimes they reach 20-30MB/s and then suddenly drop under 100KB/s

I don't have any problems with utorrent, which consistently downloads and uploads. Based on that comparison, I'm guessing I screwed up a setting in qbittorrent.
Here's some info from qbittorrent:

Windows 64
qbittorrent 4.1.5

Using UPnP/NAT-PMP forwarding
1200 maximum connections
50 connections/torrent

Rate limiting is applied to uTP protocol

DHT/Peer exchange/Local peer discovery all disabled (I cannot enable these)

Requiring encryption

Max 20 active downloads
Max 170 active uploads
max 200 active torrents

Async IO threads = 4
Disk cache = 1800MB
Max half open connections = 20

Would really appreciate any suggestions or ideas.

[Switeck]

Set Global max upload slots to 800 and per torrent max upload slots to 40.

It may be that qBitTorrent is getting disk overloads because its reading/writing logic isn't as good as uTorrent's. (qBT doesn't do grouped read/writes very well so the drive is seeking a lot.)

Disk Cache = 1800 MB? You must be using the 64bit version of qBT to be able to set the cache that high. It probably doesn't do much, but if you can spare the ram no matter.
Set the Cache duration to its max of 600 seconds, or qBT will be dumping the cache as fast or faster than it's filling it.

[Twisted]

Hrmm, I tried those things and it didn't seem to help much. Upload is still down at nearly nothing. Any other ideas?

[Switeck]

qBitTorrent is probably firewalled then and uTorrent is/was not, due to antivirus and/or firewall permissions restrictions.