Marx discusses etymology more in Notes on Wagner.
Really with Hans confirming that the word in the first edition was Formen not Formeln, I think it is clear that there was a misprint. What is interesting is that no one spotted it was a misprint. Really we are right at the edge of trying to understand what Marx was getting at.
The suggestion of Gestalt is interesting, but throughout this key section 4 of Chapter 1, the word Form is used. According to my dictionary the two are indeed synonyms over quite a range of meaning but it appears that Gestalt has connotations of shape, whereas Form embraces meanings of a container - it can mean a mould - for cakes etc. The expression for form and content is Form und Inhalt, and that contradiction is fundamental to how Marx discusses this issue in this section.
Use-value is not the problem here. It is quite clear on a middle level reading that Marx is consistent in his distinction between use-value and exchange value. The problem is that in these and other passages Andrew Kliman has spotted a more subtle contradiction between exchange value and value. I do not fully grasp the significance he sees behind this contrast, but it is not as significant as I would like to read it to be, in his opinion. It appears to be something like exchange-value is the form, and value is the content. And that exchange value form is specific to economic relations of commodity exchange. Fair enough. But if value is the content, I am irked by the suggestion that that too is limited to commodity exchange.