Is a pisces moon in my chart able to undermine all the Scorpioness?

No...but the moon does have some influence. My ex was a Scorpio sun, mercury, pluto but a Gemini rising and Sagittarius moon and he was VERY restless and could discard people easily (idk if this is a Scorpio trait too). He also loved to travel and was very fickle with things. So he had some Gemini and Sagittarius traits but you could definitely tell he was a Scorpio. Fixed signs in the sun placement will tend to dominate a personality but the other planets help. he was also a Sagittarius venus and Libra mars.