Yes it is the X-omat 2 film. I don't think the GBX chemistry is the magic elixir. I haven't tried it with any other developers nor have I tried the GBX with other films so I can't help you there. Maybe the folks at Kodak can answer that for you. I have used the GBX in my dental office for x-ray film for ages. It is good for 30 days so you could pour it into a container and reuse it several times for a month.
The film runs $111. for 50 8x10 sheets and the GBX is $15.50 for a twin pack (1qt dev & 1qt fix) they are mixed 1:3 so you don't have to make the full gallon of working sol. if you don't need that much.
Agfa has a 5"x12" film and possibly other sizes. They used to have an 11x14 film but I'm not sure if they still produce that.