On Abandoned Hall, if my spell is defied, do I still give my units plus one might?

No, you do not get to give your units +1 Might if your spell is defied (countered).

According to RiftJudge FAQ #8877 and Rule 412.1.b, a card that is countered is not considered to have been played. Because the spell never finishes the process of being played, any triggered abilities that rely on a spell being played (such as the one on Abandoned Hall) will not trigger.

This is further confirmed by RiftJudge FAQ #4905, which clarifies that for abilities triggered by playing a spell, the spell must resolve for the trigger to be valid.