Changing monospace fonts system-wide

fc-match is the utility to use. For example, fc-match monospace will tell you the font used for monospace, and fc-match -s monospace will tell you fallback fonts as well, in order. The first font on the list will be what is used in most cases, and all fonts after are fallback fonts for missing glyphs.

You have hinted the answer yourself by referencing https://en.wikipedia.org/wiki/Fixed_(typeface)

This is the standard fixed bitmap font which has been expanded by Markus Kuhn to have a rather complete character set. The question is then how to scale a bitmap.

What you have achieved so far is scaling a vector font and converting it to a bitmap (ttf → bdf → pcf). That is a fine strategy but as you mention it lacks some language support. That seems strange as Courier New is one of the more unicode complete fonts but I digress! Maybe try using Mono which is a clone.

I do however not understand why you are doing this as xterm does support truetype.

Modify ~/.Xresources such as this (note that you'll need to reload it using xrdb as seen in another answer to this question):

XTerm*renderFont: true
XTerm*faceName: VeraMono
XTerm*faceSize: 10

But back to the task: You want a larger bitmap font.

The largest available bitmap available is:

10x20   -Misc-Fixed-Medium-R-Normal--20-200-75-75-C-100-ISO10646-1

Markus have been so nice that he supplies the source BDF files. If your distribution does not have the most recent updates (from April 2009) you can grab the package directly from him.

The "-misc-fixed-*" font package:

http://www.cl.cam.ac.uk/~mgk25/download/ucs-fonts.tar.gz

Rather than converting back and forth between pcf and bdf you could/should stick to the source format. You can use a BDF font editor to resize the font. Do not expect any antialiasing or such trickery - but at least you can get a readable size.

Or you can use bdfresize by Hiroto Kagotani (also found in some package systems).

UPDATE:

I do not know of a way to scale just one window (never had the need). You could track this Superuser question. When I have had the need I have scaled the entire environment.

You can downgrade a 3200x1800 display to 1920x1080 using:

xrandr --dpi 141
xrandr --output eDP1 --scale 0.6x0.6

Other tricks for screen scaling in different window managers can be found here. They suggest using VNC:

One approach is to run the application full screen and without decoration in its own VNC desktop. Then scale the viewer. With Vncdesk (vncdesk-git from the AUR) you can set up a desktop per application, then start server and client with a simple command such as vncdesk 2.

x11vnc has an experimental option -appshare, which opens one viewer per application window. Perhaps something could be hacked up with that.