So, all but one of your points is about printing maps. You do not make clear whether these printing problems are seen on both platforms or not, I will assume Mac, since that is what I am using here.
When you Print (and hence also when you Print-to-PDF), there is a checkbox to check if you want your map sized to fit on a single page. If you want your map all on one page, you need to click that, otherwise it will usually tile across several pages. No surprises there.
When you use Export > PDF, there is no “on one page” option, because there is no assumed page size — the PDF produced has dimensions dictated by the map. If you later go to print that PDF, how that plays out is up to you and your pdf viewer. Scapple app is not involved in any troubles you have at that point. When I open and print such a pdf with Preview, Preview sizes it so as to fit my paper size, no problem.
I have been using scapple for over 6 years now and barring few issues which cropped during updates and which were sorted out eventually , I have not had a major problem with the software . It is the mainstay of a my overall work . To call it ‘amateurish’ shows that you didn’t experiment with its trial enough to see if it suits your needs. For me, this is easily amongst the top 3 softwares I use (and I use more than 50 softwares in my line of work) .