- Does this look like enough time for the connection?

Both MASWings and BI use the new terminal, unfortunately I never made a domestic-to-international connection at BKI. You will have to pass through passport control and it may take time. 70 minute connection should be doable, but you have no margin if something goes slightly wrong.

- We've got bags to check in, but I figure if I buy the BKI-BWN flight on MH, I could check them through all the way from LDU. Will this be possible?

I never had problems with Asian (non LCC) carriers to have the baggage checked-though, even when traveling on separate tickets.

- What's the reliability of MASwings like? Are they often delayed?

Assuming weather is not terribly bad, I have never been delayed by more that 10-15 minutes.