The concept of breath power I've seen in mainline Daito ryu is similar to what I have seen in Jikishinkage ryu - and I don't think it would fit the "internal" frame at all. It's pretty much about packing in a lot of power and then releasing it in some way that breaks your opponent. It could be that both systems reserve different kinds of breath training for higher levels, of course.
Yes, that's pretty much what I saw in Shin-Koiwa with Kondo. Of course, there may well be things he does that I didn't see. OTOH, there are definitely 6H related methods from other traditional Daito-ryu lines.