[RarlyL8]

Sounds like you've schooled yourself on turbo kits and how things work! The same systems and approach when transplanting a 930 engine into a 911 will apply for turbocharging your 3.0L SC engine. You've got to deal with oil to the turbo, extra fueling and systems affected by increased horsepower.
1. Yes an adjustable 930 WUR is helpful to dial in the fuel curve and for enrichment on boost. However, you will run out of fuel using the OEM SC fuel distributor and pump if adding any appreciable horsepower. We can modify the fuel distributor for more flow. The OEM pump should be changed to a -044 unit if you plan to keep just one pump.
2. Yes our headers will bolt right on to SC heads. Depending on what oil lines you have they may need to be changed. The headers will add a bunch of power and add torque to work with your SC cams allowing you to use lower boost to achieve the same results. If on a budget you can use your OEM exchangers and add a 930 J-pipe.
3. Longevity is only affected if detonation becomes a problem. Your driving style will have a lot of influence on this as well. Street cars typically aren't on boost very often or for very long periods. I do know folks (you know who you are, ha!) who drive the stew out of their turbos which would cause high intake temperatures without an intercooler, which leads to detonation.
4. MSD has a version that retards on boost. Nice option or you can just set your OEM SC distributor to 29° @ 4000rpm which should be conservative enough for 0.5bar boost at 9.3 C/R. You'll need to adjust the timing once you get some feedback driving the car.
5. I'd use a small turbo like a GT30 or similar. You'll need something that operates well at low boost levels.
Don't forget the turbo oiling, scavenging and a sport clutch.