How can I fix virtual terminal size for external monitor?

I plugged in my 4K external monitor (Dell 27 inch) to my Lenovo Thinkpad l540 running Ubuntu 18.04 using a mini displayport cable, and it works perfectly when I’m in the GUI. (The scaling option I chose makes the laptop monitor have everything too large, but that would be a separate question; it’s fine on the external monitor which is what I care about for now.)

However, in the virtual terminal, the bottom three lines are not displayed. The built-in monitor is automatically mirrored, so I can read the bottom three lines on the built-in monitor and the rest on the 4K monitor, but for obvious reasons I don’t want to do this.

Also, the text is slightly blurry (not just pixelated but fuzzy) on the 4K monitor when showing a virtual terminal. This is less of a problem than the lines being cut off at the bottom.

How can I get all the lines of the virtual terminal to show on the external monitor, preferably sized appropriately for the screen?