I am not with Laminar Research, just a flight simmer from downunder.
I have read comments in this forum from Laminar Research staff whereby when running X-Plane you should be considering using a screen size of at least 17 inches.to get a readable visual image otherwise difficulty will be experienced in reading the screen as you are experiencing
Personally I am not a Mac user but try and connect a television screen to your Mac. The screen configuration should be at least 1920 x 1080 for best effect. Television screens are far cheaper than monitors.
An alternative approach is to purchase XP11. From information supplied to me some time back from Laminar Research it is possible to enlarge the screen image to a readable size.. This ability was required when users were connecting 4K screens. XP11 has now been modified for 4K screens.
Hope this helps