Since "good" has an added "h" here (mhath instead of math), does this indicate a gendered noun? Are there masculine and feminine (and possibly neuter) nouns and cases in Scottish Gaelic?
Yep, feminine nouns make adjectives lenite, and madainn is a feminine noun, so 'math' > mhath.
Feasgar (afternoon/evening) is a masculine noun, and so 'Good afternoon' is Feasgar math.
That would make sense as it does so in Irish.
The pronunciation of mhath sounds like "va". Is this accurate?
Yes, mhath is the lenited version of math, mh makes the sound wa or va
This speaker has very good diction.
I really appreciate his enthusiasm ^^
I still find it strange to say both "hello!" and "good morning". I would say one or the other, rather than doubling up. Is this an American versus English thing?