@allen24 from looking at your current signal levels:
1. The downstream signal levels are high enough that an extra length of RG-6 won't be a problem;
2. The downstream signal to noise ratios in the upper DOCSIS 3.0 channels (1 to 32) are at the minimum. I wouldn't want to see them any lower. Having said that, the 4582 doesn't use these channels for downstream data, at least it didn't with the previous firmware version. That is something that I have to check with the engineering staff. The 4582, as far as I'm aware uses the OFDM channel entirely for its downstream data. The PLC power level is also high, which implies that the OFDM channel signal levels are also higher than normal. That will work in your favor, in terms of adding additional cable.
3. The upstream signal levels are low enough that an extra run of cable shouldn't be an issue.
Are you simply going to connect the cable to the existing cable port on the wallplate?
If you go down this path, you should use Quad shield RG-6 to protect the cable from noise.
Are there any additional cable ports in the apartment anywhere else? Typically, in an apartment, you should be able to find a wiring cabinet in the apartment that contains the incoming cable and any splitters required to connect the apartments cable outlets. By looking at that cabinet, you should be able to determine if there are any other cable outlets in the apartment, as there might be additional RG-6 or possibly RG-59 cables that aren't connected.
In terms of wifi channels, if you're using a 5 Ghz network, change the wifi channel to the 149 to 165 range as it operates at a higher power level which will increase the operating range from the modem/router. Pick a channel and leave it there, don't use Auto. Of course, if the apartment has thick concrete walls with rebar embedded, perhaps the only solution is to move the router to a close location. Fwiw, here's the wifi settings that I recommend, which are for this modem, but are generic enough for any modem or router:
2.4 Ghz wifi parameters:
Wireless Mode: 802.11 n Channel Bandwidth: 20/40 Mhz, although, for test purposes you could set this to 20 Mhz. In a crowded wifi environment, I would set this for 20 Mhz. It will default to 20 Mhz in a crowded environment. Wireless channel: channel 1, 6, or 11, depending on which channel offers the least traffic as seen with Winfi Lite (discussed below). Its possible that there's no good choice as 2.4 Ghz channels are usually oversubscribed. WPS Enabled: OFF Security Mode: WPA-Personal Auth Mode: WPA2-PSK Encrypt Mode: AES only
5 Ghz wifi parameters:
Wireless Mode: 802.11 a/n/ac mixed Channel Bandwidth: 80 Mhz, although, for test purposes you could set this to 40 Mhz Wireless channel: 149 to 165 Use this higher channel range as it runs higher transmit power levels. WPS Enabled: OFF Security Mode: WPA-Personal Auth Mode: WPA2-PSK Encrypt Mode: AES only
If you had to change any parameters, reboot your router after the changes have been saved.
When that's running select the wrench (tool) symbol in the second row from the top, near the hand side. That brings up the lower display area. Select "Spectrum" to display the graphical interpretation of the wifi network data so that you can see who you're competing with. The text data can be sorted up and down by selecting the column title. Go ahead and sort the data by RSSI, which is the received signal level at the receiving device. Have a look at the signal level of your network compared to any other network in the same channel band, just so that you know who you're competing with. Keep using that 149 to 165 channel group however as the higher power level can make a consider able difference with higher data rates, despite any nearby competition. If you walk around your apartment with Winfi Lite running, assuming that we're talking about a laptop here, stop in place for two to three minutes to let the program catch up with the change in location. Take note of the signal level of your network, just so that you know how much it changes, up and down, depending on the laptop's location.
Give that a go and see if it helps with the wifi situation.
Just to note, that signal level table can be copied and pasted into a post. Place your curser in front of the "Downstream Overview" line. Hold the shift key down and move your mouse down and to the right until you reach the last line and character in the bottom OFDMA section. You can also use the arrow keys (down and right) with the shift key held down to select that entire area. When that's done, right click .... Copy. Then in a new post, right click .... Paste. That should paste in the entire table as it appears in the modem's user interface.