As strong as Sebastian was, without prior experience with the real thing, it'd be an arduous task to be able to come out of it alive by himself or to be able to protect Sal and her nieces. Sure, I haven't seen his full capabilities but I was just simply judging from what I've seen because again… as strong as he was, their estate needed more quality fighters, not more grunts to do gruntwork.
'Well~ There's also his "personal" workers I haven't seen so… maybe? Just maybe…'
In any case, his concern for his employers was genuine because I've never seen him this anxious. However, the notion of having a tool that could potentially solve his new-found problem at the same exact time was extremely lucky and unlucky.
"So… If I managed to sink this axe on its head and press this button right after, it'll do it?"
"Yeah, hopefully..."
"But isn't sinking the blade to its head enough? I mean—"