In this case, you don't need to screw the bracket all the way in to the studs. Screwing the bracket in to the wood, which is screwed in to the studs with sufficiently long screws, is more than strong enough to hold a microwave.
Sure, in Euro-countries you can take that 3-phase wiring ("Wye" configuration, with neutral) and simply treat it as three single-phase circuits of that ampacity, sharing a neutral.
Or a 2-phase circuit and a 1-phase circuit.
So you can put the oven on 1 phase, however that will use the entire capacity of that phase.
The cooktop seems slightly too ...
There are 'lightning protectors' specifically designed for coax cable. You can put one on.
You can get a computer surge protector with sockets for coax and lan cables.
Fiber optics do not conduct electricity, so they are 'safe', but you will need to replace the communication devices on both ends, which is not free, and again those devices may get damaged....