T TocasT Tocas(TM) 50 Amp Circuit Breaker with Manual Reset, 12V- 48VDC, Waterproof (50A)

It seems to be a polarized breaker, will it work properly to charge and discharge the batteries through it? I.e. current reverses during the charge.

150A or 200A manual reset circuit breaker will be ok between battery bank and 3k inverter, using 2/0 wire? Or should I fuse instead.?

Would this 40amp be suitable for connecting my new 4000w generator to the main switchboard?

why there is more than 10% voltage drop in the Circuit Breaker ?