1) People always call Pasha a fanatic but never me !!
In seriousness, Pasha wasn't talking about supporting Ottoman Persia there, as his last sentence obviously shows us. He just wants to point out that you shouldn't overlook that sans Persia, Ottoman territory there is all perfectly doable. Yes, Ottoman Empire that still have its elite army that otherwise was butcered by Russia IOTL, can reconquer Egypt and expand to Sudan, where they can get extra manpower source to be used to expand some more to the west of it, which was and still is way less populated than Sudan. The later wouldn't be inevitable though, and that didn't happen ITTL's scramble for Africa, only after WWI. British Arab protectorates will be tad harder, but certainly still easier than annexing Persia.
2) Persia I agree won't be very holdable, but it's really more about logistic and population than religion. Sure, that's a factor, too. Thing is, you are just assuming here that Sunni-Shia relation has been always in the way Sunni-Shia interaction is running in Iraq right now. While Sunni and Shia Islam have been always two different domains, the border between them haven't always been stagnant. It was pretty fluid between Mongol conquest of Baghdad until Ottoman-Syafawi Wars. Even then after Ottomans stopped to consider Shias non-muslims, and certainly aimed in the long term for uniting both denomination under single religious authority(this was in similar way Russia was aiming for Constantinople though). Yes, Persians
will not bowing down to that, as long as they have the strength to keep standing before the Ottomans....
Yes, I agree that Persia is not annexable, but Sunni-Shia relationship ITTL 20th and 21st century can be much less antagonistic compared to OTL's case, if not very equal....