Mutations question

Quote :

tentacle
One of the mutant’s arms ends in a tentacle. He may
grapple his opponent in close combat to reduce his
attacks by -1, down to a minimum of 1. The mutant
may decide which attack his opponent loses.
Cost: 35 gold crowns

extra arm
The mutant may use any single-handed weapon
in the extra arm, giving him +1 attack when fighting
in hand-to-hand combat. Alternatively, he may carry a
shield or a buckler in the extra arm. If a Possessed
chooses to do this, he gains an extra attack but still
cannot carry a weapon.
Cost: 40 gold crowns

So, when you take Tentacle on a mutant, can he still use 2 weapons or a 2h weapon, or can he just use a 1h weapon? Logic says he could only use 1 weapon but it's not mentioned in there, and would make tentacle not that worthwhile.

Also, what if a possessed takes both Extra Arm and Tentacle? Does he get both the +1 attack and reduces his opponents attack by 1?

First question: you may not wield an extra hand weapon or use a weapon that requires 2 hands (although the carnival of chaos has a Strongman model doing this???) so I could be wrong. (Its happened before...)
2nd question: you may and they do. Much more confident about this answer.