FEMA vent interior

I have never heard of using the interior dimensions, I have always used the exterior dimensions.

No, they have to be directly from the outside to the inside.

Once I had a home that only had direct vents in the garage, and there was also a "lower enclosure" that did not have direct vents to the outside, but did have vents that passed from the garage to the enclosure. In theory, that would allow water to pass from the garage to the enclosure. I'm not sure how FEMA would view that. I noted the garage to enclosure vents in the comments section of the elevation certificate, but I did not include them in section A.

Edit: Here's a quote from the FEMA technical bulletin on flood vents that specifics exterior walls:

http://www.fema.gov/media-library-data/20130726-1502-20490-9949/fema_tb_1__1_.pdf

"Each enclosed area must have a minimum of two openings; if there are multiple enclosed
areas, each area must have openings in its exterior walls,"

My short answer is no, interior walls shouldn't count. However, I can't really think of a situation where this has come up for us other than an attached garage.
But we do these all the time with attached garages. Especially in the Lakeview neighborhood of New Orleans, the garages will be on slab and the house will be a few feet up with a crawlspace. We have also had some like "Pseudo Ranger" just described, where the only vents from the garage are into the crawlspace. The only difference is we do include it in section A9. However, in this case, we will make sure the vent total of the whole house will cover the garage SF also. Either way, we usually try to note it in the comments section.

Thanks! It's a building diagram 6, so the enclosure below is not technically a garage. (it's just used for storage.... of a car!)

Does it have break a walls? Just in case you need a fast get a away and don't have time to wait for the garage door to open?