The CPU may be your problem, depending on its number of cores. I don't think you will get these maps to work with something below a quadcore. The next thing might be V-RAM. The higher, the better.
I'd assume RAM or V-RAM, CPU problems would have been obvious at an earlier stage of the game, it might be tho (at least in my experience) that with simulation games that need a lot to be computed (ludicrous size probably needing about 20-30 minutes on a 2ghz laptop processors with four cores) that windows thinks that the game or application hung up while in fact it didn't (factorio with tons of mods, kerbal with tons of mods, mods with tons of mods and other things show this behaviour, I remember producing a dwarf fortress map on my notebook that took 25 minutes, while creating a far bigger map with 20 times the history length only took my dualcore (back then) 15 minutes)
but unless his cpu is missing certain instruction sets (which would make the game unstartable) it's doubtful to be a CPU problem
RAM at first glance seems okay, but if ludicrous size takes up to six gigabyte (private bytes, at least for me it only tends to have 2gb+ working set on 192x120)
it might be too much for his computer, win8.1 probably using well over 2gb already plus all the other small mods
if he has a laptop gpu solution with borrowed vram then it just won't be enough
anyhow trying out the map
also I think the dynamic or simultaneous turnphase would benefit the turn time a lot
sadly I haven't found a way yet to get it to run in sp (even when replacing all references and settings with the multiplayer ones and/or enabling it for singleplayer in it's own option)
the downside is obviously a short hang on each turn when all the city states and others move their armies