I'm not too familiar with Expositiones Mathematicae, but have you given them a look?
EDIT: The article I happened to have seen, which made me think that Expo Math might be along the lines Pete Clark was looking for, is this paper of T. Bühler - it modestly claims to no originality save for assembling disparate parts of the literature and writing down what's old news to connoisseurs (I'm paraphrasing here!) but of course this is, in a sense, precisely its originality & worth.
As this may be of use to others as well, I will try to provide some general points on journal selection for an `average' paper.
One obvious general approach to take is (i) to look where the references of your paper were published (and I note that there are lots still unpublished so here that may raise a problem... so check on whether they have now been published).
(ii) Look at, or estimate, the publication backlogs where available and make your decision on those grounds. (You have a delicate balancing act ahead as your idea of a two month acceptance is really hard to achieve and may need revising!)
(iii) Look at other journals similar to those found by (i), e.g. by iterating (i) on the recent papers in your reference list. Electronic journals tend to be quicker to publication, and probably also to acceptance, than traditional ones, of course, so (ii) will be biased in that direction to some extent.
(iv) Finally I have not read the introduction to your paper but often introductions are crucial in 'selling' a paper to the referee. If you say what the paper sets out to do, clearly and concisely, then your chances of getting a referee's report more quickly, and one which will be positive, will increase.
(v) The paper was submitted to Arxiv last November. That means you have a certain distance from it. Do a critical health check on it from the point of view of wording, sentence structure, spelling, etc., before sending it to any journal. Get a friend or colleague to do a quick read of intros etc. so as to get a second opinion on wording. Think of the poor referee, make their job easier. They need to be able to evaluate the paper fairly quickly. Check, yourself, for typos (and, of course, don't trust spell checking programs on this). My reaction to writing a report when there are clearly lots of typos is to put it off for a few weeks... therefore longer turn around time.
Finally I feel that your should have put the question in a different form. Specific journal suggestions are hardly the responsibility of MO but your general point on how to select journals for such a paper is a valid one .
Best Answer
If you have numerical evidence in support of the conjecture, the journal of Experimental Mathematics seems to fit the bill:
Several publications in that journal have gotten quite some traction, like:
Mahler's Measure and Special Values of L-functions
New Conjectural Lower Bounds on the Optimal Density of Sphere Packings
Kashaev’s Conjecture and the Chern-Simons Invariants of Knots and Links
About a new kind of Ramanujan-type series