grammar - Help understanding いいやって and いやだなって

I'm confused about the parts in bold in the sentence below:

山田みたいに、ぜんぜん勉強しなくていいやって、わりきれるわけじゃないわりにはそれほど勉強しないし、怒られても気にしない性格じゃないし...すごくいやだなって思ってるのに、ついつい怒られているよ...ああ、最悪の人生だね。

Like 山田, I don't study at all ??? It doesn't mean that I'm satisfied with not studying that much, and I'm not the sort of person who doesn't care about making people angry...even though I think it's really unpleasant ... unintentionally making people angry ... it's the worst life (my translation attempt)

My best guess at what いいやって means is "play well and..." but shouldn't that be よくやって?

As for すごくいやだなって, I'm assuming って is the quote marker for 思う. And いやだな is just いやだ (it's unpleasant) with a な on the end for emphasis.

Also, my translation of "even though" for のに seems a bit incongruous.

Please explain any errors I have made.

Answer

I'll elaborate on the いいや.

From 大辞林:

や

㊃（終助）② 軽く言い放つような気持ち，または，なげやりな気持ちを表す。

「まあ，いいや」 「今さらどうしようもないや」

The 〜や adds an “oh well” or a “whatever” kind of sentiment. You use it like you would use 〜よ, but to yourself and with a sense of resignation.

いい can sometimes be safely translated to “don't mind”, but perhaps it would be easier to just think of it as an “okay”:

A: ここ座っていい？ (Is it okay if I sit here?)
B: いいよ (Okay)

Then, when you're telling yourself that something is okay, you might say:

このベンチ汚いけど座っていいかな？ いいや、座っちゃおう。
This bench is dirty, is it okay if I sit? Okay, what the heck, I'll sit.