1)when playing with the extension something wicked an the coast, when a card from the base game request to refer at a Town Item (example card mystery "late night experiment" or lair card " blacksmith" value 3)is what the card Monastery item and coastal item are egal to town Item ?
Yes, generally a reference to Town Items refers to any and all of the three stacks.
2)The capacities "Corruption and madness" of the unspeakable horror said :"on the roll of 3 or 4 the elder immediately joins the villain as an evil elder" all right but that become the secrets cards of the elder. Ignored or applied ?
When a Town Elder becomes Evil his secrets are revealed. There are a couple secrets, such as "Darkest Secret", that would stay with the Elder while he is Evil. Any other Secrets get discarded.