Thank you for your input.
This might simply be an issue of parsing an incorrect number to the web interface as querying the same signal values directly from the modem using AT commands return reasonable numbers. However, this does not influence the connection quality.
As for the antenna connectors, it does not matter, which ports you connect your antenna connectors to as they all operate identically. The same applies for WiFI connectors. V and H simply indicate that the signal is forwarded to either vertically or horizontally polarized element of the antenna, which have different propagation features.