Compression Fittings (SIF's)

I am working on 1/2" tubing (3,000 psi @ 670°F) and would like to know if anyone has any experience with calculating SIF's for the fittings?

The tees are welded so I plan to use Item 3- Welding, is this acceptable?

How about elbows with compression fittings? They look more like a square. Do we just model a rigid?

Thanks all!