～たって

I think I understand the meaning/usage, but just to make sure:

彼女にいいとこ見せようたってそうはいくかってんだ = 彼女にいいとこ見せようとしてもそうはいくかってんだ/彼女にいいとこ見せようといってもそうはいくかってんだ？

1)I'm pretty sure it's this usage: たって, I assume 意向形 (～う/～よう）is considered a 助動詞, but according to the usage rules: 「名詞、活用語の終止形、動詞と一部の助動詞の命令形、一部の助詞に付く。」It can only be used with the 命令形 of a 助動詞? Or is the entry simply ambiguously worded?
This structure is definitely grammatical though, there are even dictionary entries with ～よう/～う＋たって: #sentences ようたって - Jisho.org

2) This part "助動詞の命令形". Is it referring to られろ/られよ/せよ/せろ/ませ etc.?

2a) F.E. can たって be used like this: 「壊れろったってそうは行かない」?

1)
見せよう belongs to 活用語の終止形.
動詞と一部の助動詞の命令形 means 動詞の命令形と一部の助動詞の命令形. I think it's because only 一部の助動詞 have 命令形. (I can't think of any 助動詞の命令形 that can't be attached to （っ）たって now.)

2) 3)
Yes.

Thanks. Yeah, I understood that it means the 命令形 of both 動詞 and 助動詞. There was even an example sentence including a 動詞の命令形: 「来いっ―すぐには行けない」
I just assumed that (見せ)よう is considered a 助動詞. That's why I only asked about "命令形 of a 助動詞". Now that you've explained that it's considered a 終止形 the usage makes sense.

BTW, if I re-word the sentence like this:
「動詞そして/または、一部の助動詞の命令形」 or simply 「動詞、一部の助動詞の命令形」
Does the 「命令形」 only modify the 「一部の助動詞」 part now?

～よう indeed is 助動詞 in 国文法 / 学校文法. 助動詞 belongs to 活用語, therefore 活用語の終止形 contains 助動詞の終止形.

The meaning doesn't change from the original.
名詞、活用語の終止形、動詞の～形、一部の助動詞の命令形 can express what you want to say. 名詞、動詞、活用語の終止形、一部の助動詞の命令形 works as well, but since 動詞 usually expresses the entire conjugation forms of verbs, I don't think there actually exists such kind of expressions/structures.