My opinion is that both the Surface Pro and the iPad are Toaster and Refridgerator type devices. Tim Cook tries to be critical of the Surface Pro while trying to emphasize that the iPad is a tablet that can also be a laptop replacement. Apple sends a very mixed message about the iPad. On one hand they try to claim it isn't a refrigerator/toaster type device like the Surface Pro. Then they say it can be a laptop replacement. Then they have an ad with a kid enjoying his iPad and the mother asks him something about whether he is enjoying his "new computer," to which the kid responds "Whats a computer?" OK Tim, is it a tablet, is it a computer and a possible laptop replacement as you suggest? Or is it not a computer as your ad suggests? You can't have it both ways... unless it's a toaster/refrigerator device also
My own opinion having a 9.7" iPad and having tried the cycle of 12.9 iPad Pro, to Surface Pro, back to 12.9 iPad Pro thinking I missed the Apple ecosystem with that, back to Surface Pro because I missed that device more, is that they both have toaster/refrigerator elements to them. The Surface Pro is more refrigerator and a little toaster. It is basically a lightweight and mobile laptop, which can be used as a suitable tablet device between the touch screen and the pen. The iPad Pro is primarily a toaster (tablet device) that can at times be used as a laptop replacement (refrigerator). The question is what is your primary use? Do you need a refrigerator with a toaster slot or a toaster with a mini icebox
For me, I needed the small and lightweight laptop device primarily that could also be used as a tablet, can be charged in the car with a 12v adapter, be able to have people sign documents with the pen, use for powerpoint presentations, etc. The Surface Pro works much better for me.
In answer to the questions:
1) Absolutely the Surface Pro can use full desktop programs. Surface Pro, unlike the Surface Go, comes with Windows Pro 64-bit standard. The Go can also run full desktop programs, but you need to make a switch in settings to go from 10S to Pro.
2) Surface Pro includes its own antivirus called Windows Defender. It is all I use. I update it daily and haven't had any issues in the year I have owned it, but I also don't surf the dark web. There are more robust solutions available if you need them for both PC and Mac.
3) I had to exchange my first one, not unlike many Mac purchases I have made. There was an issue with that one where the keyboard kept freezing until I detached it and re-attached it. They swapped the keyboard first and that wasn't the answer. This one I have had a year and it has been flawless. I purchased it as a business purchase (only a business card needed to set it up) and added a business warranty (Microsoft Complete for Business ) that can be up to 4 years in length and includes two incidences of accidental damage with no deductible. A 4-year plan is $399 for the Surface Pro.
Setting up as a business also gets you discounts on the device, accessories, service plans, etc. I think they are the same as the educational discounts.
https://www.microsoft.com/en-us/surface/business/extended-service-warranty