Do you recommend to update the firmware?
No need to do it, if the miner is working ok.
My temp at the chip is showing about 70-75, is this a good figure?
Yes.
The error rate is about 0.0006% (bottom of column DiffA#, right?), is this acceptable?
Yes, not bad at all.
And at the pool settings: Do you recommend setting three or two different pools or just my first choice pool with different ports? (Pool recommendations are welcome at this point, I'm still trying Slush, ViaBTC and BTC.com)
You can use your first choice pool with different stratum addresses.
So if you mine at Slush, depending where do you like you put the US address first, then the Europe address and then the China.
Here is an example:
Pool 1 stratum+tcp://us-east.stratum.slushpool.com:3333
Pool 2 stratum+tcp://eu.stratum.slushpool.com:3333
Pool 3 stratum+tcp://cn.stratum.slushpool.com:3333