Formatting Windows too?
Yes.
Are how many activations?
As explained on our site, you have 6 activations per order.
If I need to change processor or video card, consume activation?
Processor, most likely Yes. Video card, most likely not, but it depends on the video card you are upgrading from and the one you are upgrading to.
If you reach the maximum limit of activations, loses license?
Obviously not. As indicated on our FAQ page, if your last activation was issued more than 90 days before, older activations will be reclaimed to get new ones after the 6th, automatically. And if it wasn't, you can always contact support by email, asking for a manual reactivation.
If I disable the GSX also loses activation?
If with "disable" you mean the "Deactivate" feature of the Addon Manager, the whole point of it is that you will remove one used activation so, after you reactivate on a different system (or an upgraded one, or a reformatted one), it will compensate the new one you'll use on the new system, netting to zero "consumed" activations.
Is there another way to disable GSX, besides FSX?
No, you must access the Addon Manager. But, you said it's your FSX that has stopped working so, if this can be fixed by reinstalling FSX, this won't use an activation.
But why are you so worried about activations ? Are you SURE you already used all your 6 ? And even if this was the case, what's the problem ? You'll get a clear message such as "too many activations" when you'll try to reactivate again, so you will simply have to contact us asking for a manual reactivation.
Don't see how this is any different than reactivating FSX, or Windows itself, if you exceeded your FSX activations or your Windows activations, you'll have to contact Microsoft (by phone) and you don't have as many as 6 activation with MS products.