A few factual points, because in my opinion there is a lot of unnecessary aggressiveness here, but the OP is rightly seeking help.
a) The area (Palatinate Forest) is one of the poorest regions in Germany (Pirmasens district not far away is the bottom in West Germany). Accordingly, land prices are low and house prices are also dirt cheap. This obviously does not apply to new builds (what a surprise), but the purchase price is therefore not suspiciously low.
b) A quick look at the train app shows that the town is connected to Mannheim every half hour by S-Bahn (travel time about 50 minutes). However, this is not really a contradiction to a). Because the S-Bahn connection might be a criterion in the south of Munich, but not in the Palatinate Forest. People simply don’t want to go there. There is simply nothing there. Life only begins below Neustadt or Landau. The Palatinate Forest is deserted and breathes a morbid charm. That is why I agree with the bank, which considers the purchase price (albeit for another house) more as too high than too low. A plot of land there with an existing building on a railway line, which a homebuilder would first have to tear down, has rather a positive than a negative value. If you move to such a dump, it is usually to build a new little house in a nice location with an SUV. Therefore, the mentioned property should not meet with widespread approval.
c) The OP has no car and works at a train station (in Mannheim?) and would probably still be able to get to work reasonably. If not: caution. Buying a house that leads to a job loss is harakiri. But what about the husband? Does he also continue to get to work (even if only part-time)? For this, 50 minutes one way is probably too much. Are there possibly jobs in the region (Neustadt?) reachable by train that are worthwhile even for part-time?
d) Please make clear to yourselves that he lives in the middle of nowhere and while the S-Bahn regularly gets you to work, social life is certainly noticeably more difficult. On the other hand, maybe that is exactly what you want if the city no longer feels safe to you?
e) Please do not underestimate the renovation. Do you have experience with that? How do you want to manage that without a car and driver’s license? Here I see the big snag. Unless by chance the electrical system and water pipes were done in the last 30 years, this can become a bottomless pit. It is then no longer a matter of tens of thousands, but quickly hundreds of thousands of euros (the facade will also have to be done sooner or later). With your wealth/income you can hardly rely on external craftsmen. So I fear that even if you agree with a-d), you will have to renegotiate the price again. Also inform yourselves again about subsidized loans. You have 3 children, so there should be a cheap loan (in the 1% range) at a promotional bank (e.g. the L-Bank in BaWü, I don’t know about R-P). They also make sure that you only get this if you have the creditworthiness for it. I understand that for floors, wallpaper etc. the cheapest is enough for you. But if the pipe leaks, that no longer works. If the heating has to be replaced by a heat pump and the house doesn’t get warm anymore because the facade is not insulated, likewise. These are points where unfortunately you cannot save.