Seems like he assumed the explosion was going to be like the one that went off when the 3 adventures stole the rings that detonated in his realm. But that one was being contained by tomoe offshoot's barrier, the alkey's defense and the clay aegis the adventures had. So instead of the suppressed version he knew of they got the full blast one.
Not yet, they'll come back only to get killed for real, the boy, who's a dragon turns into an egg and is put into the custody of another dragon, while the woman if I'm not wrong gets killed and reincarnated by the femboy dragon, but she has her memories completely wiped and she's put to work as an adventurer for Makoto
Makoto cannot speak human/common language. Anything he said only sound like gibberish to Sophia. The kid is not human. And he is too panicked to use magic writing