「あの[洲]{す}よか、こっちっ[側]{かわ}[中心]{ちゅうしん}に[攻]{せ}めるってことでねー」
- How the second line translates? Literal translation is preferred as I'd like to understand every bit of this line.
"So, we/I should concentrate our/my attacks on this side of that sandbank, eh?"
「よか」 is a more informal form of 「よりか」, which is already informal. The more formal forms are 「より」 and 「よりも」.
- What's the reading of 側 here?
It is 「かわ」 unlike what was said and even upvoted in the comment above.
If it were 「こっち側」, then the 「側」 would be read 「がわ」.
- What second っ in こっちっ does here? Is it an accent/colloquialism, or does it stand for something?
The small っ makes it even more colloquial/informal. This can be said about so many other words as well.
In the order of formality: こちら側 ⇒ こっち側 ⇒ こっちっ側