I agree with Tim, let the condition of the pistes be your guide more than what tyres you have.
Last November I hired a 650 Husky with Tourances and was surprised how well it managed the albeit dry, stony pistes, considering they're effectively road tyres.
The luggage was in a car and obviously one rides appropriately, but that's still a heavy bike.

Go on what you have, head south to enjoy the empty roads and the dry desert pistes with little sand. If you leave on new tyres they may well last your whole 3 months. I don't think I'll be getting TKC ever again: K60s will do me.

Pick a piste that's short and manageable like the crossing from Akka to Imitek (start of MA3) or the flat ride between Akka Ighern and Foum Zguid (MA9, maybe already sealed). Great roads all round there too. Or the short MW routes around Tadait (Assa). Perfect for short off-highway excursions providing it's dry.

Even the popular MH4 over Jebel Sarhro ought to be doable, certainly from the north coming down to Iknioun (mostly wide dirt motorway atm) where you can nip up on the piste to the pass and then come back and take the tarmac road back north to Dades if you don't fancy the ride down to Nekob.
Another good place is simply gunning around off piste on the flat gravel west and north of Merzouga, away from the dunes.

All you have to remember is that if it all gets too gnarly simply turn back and go somewhere else.

Let us know how gf gets on with the 500X - that looks an interesting travel bike.

Ch

Another vote agreeing with the above two. Your road oriented tyres will get you a long way offroad. Due to questionable planning I ended up riding alot of gravel (and offroad finding camps) on a fully loaded bike with a 100% road rear tyre. Not optimal, but no big problem either.

So plan to do the routes you want, and if it turns out that you don't feel comfortable on them, you can turn back and find a better road.

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Vladivostok - Denmark 2008... Finished.
Denmark - South Africa 2010-2011... Finished.