"アダッ" doesn't mean "needle fish", it's simply a yell when Kazuhiho's in pain when his foot got stomped, "Ouch!" is sufficient to use here. "おぶッ“ also didn't mean "pig", it's also a reaction from being hurt, like "Ugh!". Small tsu "ッ" in the end of a word of sentence simply means it's a chocked sound or glottal stop, you don't vocalize the 'tsu' there, you've to differentiate that from big tsu ツ.
ご近所付き合いなんて初めてだからねもう予約してあるのさ
Can simply be translated into "Since it's the first time we hang around like this, I've already made a reservation."