Yes, I find violin-style bows are not great for bowed psaltery. I would recommend the psaltery style bow.
I can’t speak to the Nederland strings directly, but I’ve no reason to doubt their quality. However, the instrument I have was strung with multiple gages of string – this is what is meant by scaling, how you choose the gage for the length of string for a given pitch. Wikipedia has a good intro article. Most primers on the topic are aimed at guitar players, but the principle applies to any string instrument with more than a few strings or range beyond an octave or so. Short version is that you need to get the scaling right to keep from breaking strings and/or ruining your sound. Again, I’d refer you to the Music Maker’s kit manual linked above.
“Alt Hoch” means “old high” in German. Could be just the brand name or might have a more specific musical meaning in this context; not sure.
 Also, I don’t know of anything inherent to the construction of a bowed psaltery that puts the instrument’s integrity at risk when you take all the strings off. If it’s build like the ones I’ve seen, it’s a framed box with a skin (the soundboard and back), so, like a guitar, it should be fine with no strings. I’ve seen people just cut the strings with wire cutters when restringing.
Last, you can, of course, string one of these without ball ends on the strings, but ball ends make it way easier. Stringing any zither from bulk string takes some skill, so if you decide to try that, be sure to research tying techniques.