As Matagui mentioned, ヒモ as in pimp/leech is always written in katakana, just like other sex business terms are. So all instances of 紐 should be replaced by ヒモ.

Secondly, when the word ヒモ is used as a metaphor like this, it is usually interpreted as the "lazy leech" version, not the "brutal pimp/slaver" version; The man who relies on X for a living is not working at all (or little to no income), but X is spontaneously making money for him (so he can continue being lazy). That being said, if you are actively writing some professional stuff right now, that doesn't sound like a ヒモ type of living to me. Regardless of how cruel you are for milking the money out of words/language.

1) 言語のヒモ 3) 言葉のヒモ

Both don't really refer to writing, unless contexts are given that you are a writer. Even then, this is a way of saying you are a lazy writer. 言語 may be too formal/academic feeling (dictionary comes to mind), whereas 言葉 is a speaking oriented word rather than writing.

It should specify what allows you to get a living without work. For example;

印税のヒモとして生活している

I've been living on the royalty payment from my books. (implies not writing anything for long)

2) 言語ヒモ 4) 言葉ヒモ

Doesn't make sense. It rather sounds like... what type of strategy you use to trick a woman. (by word/witness vs appearance/age etc)