The instructions to use SNA are available in online tutorials and videos. The user can get them at articles-faq
- specifically, should check these 3 tutorials:
* How to: SNA Measuring RF Filter response: Measuring RF Filter Response Step by Step
* How to: SNA Measuring Reflection - Return Loss: Measuring Reflection Return Loss
* How to: Measure Directivity of Directional Couplers: Measure Directivity for Couplers
The software covers the full 6GHz range and not sure why it showing for you up to1.2GHz limitation. Could you please check the tutorial?
To the last question: adding a power rollback is anything but simple in a handheld device, not mentioning distortion introduced. The SWR is not a problem when using low power modes (-30dBm output and lower) which are the recommended setup for normal use with the analyzer, so in other words, it is a note of caution but should be not any problem under normal usage regardless SWR.
For the 50ohm load, you can purchase the 50ohm termination.