How to go on?

You do not want to be part of the embarrassing academic farce here represented? Yet at the same time you plan to deal with the issues with which the so-called "speech-act theorists" deal--communication, speaker meaning, linguistic meaning, institutional facts, etc.? Then here is what you can do to belong to the good ones:

(1) If you hit upon a term like "illocutionary act" (or "speech act" (or "illocutionary force", or "illocutionary mode", or ...) in a writing, make sure you know clearly and precisely how it is is defined, or used, in that text.

(2) In many cases you will find no definition, and be unable find our precisely what definition should be applied. Often, authors shift, unawares, between different conceptions of "illocutionary act" (such as, for example, when they deal with different accounts without perceiving that the conceptions adopted in these accounts do not correspond). Often, authors do not define the term at all, and actually have no identifiable conception of "Illocutionary acts" (because their conception is too vague, or ambiguous). In such cases, be aware that the range of phenomena which the term could be referring to is multifarious. Do not arbitrarily presume a conception, when you have no convincing reason that it actually is the one applied by the present author.

(3) If you use any such term in your own texts at all, define it precisely and clearly, and stick to the definition you gave. 

(4) If you want to be on the safe side, however, simply do not use terms like "illocutionary act", "illocutionary force" (etc.) at all! Because even if you define them clearly, most other authors will still confuse or intermingle your use of the term with the use of others--after all, the polysemation problem is largely unknown.

(5) But how then refer to the entities you want to refer to?--In fact, in most cases there is a very easy answer: for "communicative intentions" use "communicative intentions", for 'successful communication', use "successful communication". For 'mean ... by an expression' use "mean ... by an expression". Simply use suitable natural terms to express what you mean. For the sake of clarity and precision, give clear and precise explanations (the terms "locutionary act", "illocutionary act", and "perlocutionary act" definitely do not contribute to either clarity or precision).

If there is no natural term at hand for what you aim at, you may of course introduce a new technical term. Yet define it (a) explicitly, (b) precisely and (c) ostentatiously--in order to spare them the miserable fate that occurred to "locutionary acts", "illocutionary acts", "perlocutionary acts" and "speech acts".