Hi,
Film is not "shot at" an ISO. It is "shot at" an EI. The ISO is a physical property of the film, and is pretty well fixed at around 1000, give or take. The EI is not a physical property of anything, but what you tell your light meter you are using. What you are really asking is what EIs work best.
So, it can be assumed that it is an ISO 1000 film, and I think the data sheet actually says that 800 is better, for some reason that I do not remember. As far as what EIs to use, approach it the same way you would approach rerating any other film. Rate it at 1600, and you underexpose by a stop, rate it at 3200, and you underexpose by two stops, and so on. (It does the same thing as rating Tri-X 400 at 800 or 1600.) Then develop to suit.
All b/w developers will work with this film. If you want as much speed and contrast as possible, I would stay away from gentle developers like Perceptol. You should just go ahead and use whatever you already have on hand.
ISO refers to one of thousands of different standards mandated by the International Standards Association, in fact Black and White still photography film speed is ISO standard 6:1993 there are other standards for colour reversal films, colour negative films, aerial films, radiographic flms and others . There are close to 100 different ISO standards for photography. The standard is 6 pages and details the methodology for determining film speeds, I haven't read the standard myself (you have to buy a copy), but like any other ISO standard, the manufacturer needs to document every little thing in order to be able to call it an ISO speed. Some manufacturers follow the older ASA or DIN standard methodologies, where the result is an equivalent to the ISO standard methods.
Changing any one or more factors may give an acceptable result, but isn't following the same methodology as the standard, and may not be the same as the measured result for ISO, you would refer to it as an Exposure Index. For example if Kodak documents that they used Tmax developer for the recommended time then using D76 for the recommended time, even though you get the same speed, it's an exposure index, not an ISO speed. Yeah ISO standards are very pedantic and detailed. Note that the standards are actually different for B&W, colour negative and colour reversal films, because they have different standard numbers.
Films like Tmax 3200 and Delta 3200 have a given ISO speed, IIRC ISO 800 and ISO 1000 respectively, but can easily be pushed to 3200 following the manufacturers directions, results are acceptable, but are not the same as the result that would be required for ISO 3200 film, so we would call 3200 an Exposure Index.
For those interested, there is an ISO standard for digital, this would be the ISO speed for the sensor, by varying certain things electronically and digitally you can push or pull to other speeds, and get an acceptable result, that, also would be referred to as an exposure index.
