OBS can't hit 2.5Mbps Upload, neither can Ggle Speed Test, but Spectrum says my 20Mbps upload speeds(I pay for) are fine?

Post screenshot of SpeedTest i think you are mixing MegaBits and MegaBytes.

Have you tried a different twitch server? Sometimes they kinda suck. Switch to another one close to your location and see if this fixes the issue.

I would personally call your provider and ask Why is my upload speed slow? It may be from their side or from your side,
First i would update Ethernet Driver from motherboard manufacturer site, if you have Asus Turbo Network software or any other uninstall it.
"Method 2 Release and renew IP address.

You may also follow these steps and check if it helps.
a. Press Windows key + X, Select Command Prompt (Admin) and then press ENTER.
b. At the command prompt, type the following command and then press ENTER:
                ipconfig /release
                ipconfig /renew
c. Close the command prompt.

Method 3 Reset TCP/IP settings.

a. Press Windows key + X, Select Command Prompt (Admin) and then press ENTER.
b. At the command prompt, type the following command and then press ENTER:
                netsh int ip reset c:\resetlog.txt
Note: If you do not want to specify a directory path for the log file, use the following command:
                netsh int ip reset resetlog.txt
c. Reboot the computer.


Method 4
In some instances, the IP settings or network configuration that you receive from your Internet service provider (ISP) might be incorrect or need updating. Sometimes, the connection between the modem and the ISP might experience problems. To update the settings on the modem or the router, reset (restart) the modem. This creates a fresh connection to the ISP. follow the below steps to reset the modem settings.
Disconnect the cable that connects your computer or router to the modem. This can be either a USB cable or an Ethernet cable.
Turn off the modem using the power switch on the front or back of the modem. If the modem doesn't have a power switch, disconnect the power cord from the back of the modem, or unplug it from the wall.
Wait several minutes, and then turn on the modem and reconnect the cable from the computer or the router to the modem.
Restart the computer
Test your connection to see whether you can access the Internet."

Sorry if i doubted you with "i think you are mixing MegaBits and MegaBytes." some people are mixing it.

Spectrum's speedtest and Speedtest.net are both owned by ISPs, so the ISP detects a speedtest is happening (especially their own) and has it report a fake number, or they just give it the special priority it needs to get a good result.
https://fast.com/en/ is run by Netflix, so they actually care whether your speeds are accurate or not, but only do download speed.
http://www.dslreports.com/speedtest is a bit more neutral.

Have you tried a different twitch server? Sometimes they kinda suck. Switch to another one close to your location and see if this fixes the issue.

uhh well, what are your OBS settings?
Twitch has like a "max" bitrate of 6000 anyways, and if you're on variable bit rates, it may be you're only need 2500 for your settings.
https://stream.twitch.tv/encoding/
https://help.twitch.tv/customer/portal/articles/1253460-broadcast-requirements

If you are Broadcasting to Twitch with a recent version of XSplit or OBS, you may have noticed the option to select between VBR (variable bitrate) and CBR (constant bitrate). Twitch suggests that all Broadcasters use CBR for several reasons, all of which relate to the final quality of service (QoS) that your viewers will experience.

The main problem with VBR is during lulls in the action: paused games, hero selection screens, even famous talking heads. During these sections of video, VBR streams produce a significantly lower bitrate, which can cause issues on pretty much any end-user connection when the bitrate spikes back up during the action (team fights, Protoss vs. Protoss battles, 2GD petting Victory Cat). This is due to interactions between multiple RTMP, other TCP streams, routers, buffers, and a whole complex morass of tech buzzwords.

VBR also leads to issues when sending data to the Twitch network over many ISPs. When connecting to Twitch, the route your ISP takes may not be stable enough to handle sudden increases in bandwidth, leading to “broadcast starvation.”

Broadcaster starvation (instability) is when video data is not arriving on time, or completely missing to twitch servers. This happens when there are network problems between you and twitch, when you attempt to stream at a bitrate that is too high for your network/isp, or have problems with your router causing frames to be dropped before entering the Twitch network. This leads to lag for everyone including people watching on your lower resolutions, buffering, and stream disconnections.

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