First, let me warn that I believe I have this condition, so that's not the best time to ask me to do anything (other than just giving up on something: that will be very effective!)
Creating an app is a lot of work, especially for one whose job is in a different aspect of software development. Especially the user interface is the most tedious, painful, boring, time consuming and difficult part to get it right. So if you are looking to my app to be user friendly, look elsewhere: there is no chance I can make one that way (and nobody volunteered to take that aspect of the job).
Moreover, while superficially similar, PM and my app are very different. The former tries to teach sight reading by throwing music at you, mine would be instead a long list of curated exercises in progressive order, vaguely inspired by the various books I mentioned in the other thread. At the moment I have implemented only the most basic exercises, and the user interface is non-existent (that's why the app is not available in the app store: I can send the binary to anybody interested in side-installing it, but there's no user support).
Also on feedback regarding good-or-wrong notes, PM provides it at the end, whereas mine provides it on-the-go. Additionally, PM has accompaniment, so it may be an experience similar to sight reading in a performing context, whereas mine at the moment does not even have any rhythmic aspects, and if/when it will, it'd just be a metronome. Finally, they are a company with money and staff. I am somebody doing things for myself (and asking if others would be interested): what they can develop, test and implement in a pay period of two weeks (80h of professional work) it'd take me at least twice (160h) of amateur work. At an average of 30m per day (since I have a daily job, a wife, homeowner chores, trying to learn the piano etc) it will take me a year to do the same thing. So, if you like PM and are looking at my app because of the problem you describe, you are throwing away the baby with the dirt water: don't do that.
I am sure the paid version is identical to the trial and does not have the feature you seek. But, there must be ways to enlarge the size of the thing that are easier than developing a competing app: a larger monitor, separate magnifier glass app (on linux those duplicate the content of one window in another window, but with a magnification -- if that does not exist in your OS, ditch it) or asking the PM people. In fact PM is continuously implementing subtle and not-so-subtle changes and they seem to be responsive to requests.
After all of that said, I can say that the way that I render the score in my app is using a vector graphics library and as such it can be easily and blur-less-ly (if that's a word) scaled to any size one wants.