Well, those ELOs again!
I have won and lost many blitz and correspondence games with 3. c4, but I have faced it OTB only a few times (4-5 irrc), as I didn't participate in many tournaments and moreover my opponents have chosen a variety of answers to my 1. e4.
In OTB games I was always achieving a good position with this Anti-Sicilian (3. c4), but this may have been due to reasons which are irrelevant to the system itself: a) I play the Sicilian as Black so I understand it quite well, irrespective of my theoretical knowledge as White, b) a really strong clubmate of mine (~2300) used to play this system and took some time to explain to me some of the finesses, and c) in most of these OTB games my opponents had started with 2. ... d6 and then chose to defend a Maroczy Bind, which is not the usual cup of tea of a Najdorf, Dragon, etc. player. So, the system does have some surprise/practical value.
Now to answer your question I would like to guess some statistics:
a) Let's assume that you have some time to devote to the openings and particularly to the Sicilian from the White side (otherwise continue with the Alapin for the time being and study endgames, etc.);
b) Let us also assume that you face the Sicilian in about <35% of your serious games (be it correspondence or OTB);
c) From those Sicilian games I also suppose that about 40-45% is 2. ... d6, 40% is 2. .. Nc6 and only 15-20% is 2. .. e6. So, counting also your games as Black, we are talking about 50%(White)x35%x15% = 3 games in 100. So maybe for the time being it is not worth it to learn the Open Sicilian against all these 2. ... e6 systems you have mentioned.
Moreover, for me it is either you learn and play only 1 Anti-Sicilian (e.g. the Deferred Alapin against all, or 3. c4 against all) and then gradually introduce the Open Sicilian (and I would start from 2. ... d6, as it is the most popular), or you start playing the Open Sicilian right away and see what happens. This may be less fun, but saves a lot of time.
What seems like a lot to me is that you have tried the proper Alapin, d6/Qxd4, Nc6/Bb5 and also need another Anti-Sicilian against e6. I am inclined to suggest a rather radical solution:
i. Keep d6/Qxd4: it is an Open Sicilian and a good, sound alternative system to know;
ii. Start studying the Open Sicilian against Nc6 (Classical, Taimanov, Sveshnikov and the rest);
iii. Do not study anything against 2. ... e6 and play (intuitively) the Open Sicilian whenever you face it.
You may want to change the specifics above but I hope you get the idea..