I am not a doctor or expert.
The medium probe is only used for obese patients. For ordinary patients, I believe the standard probe should be used. I have not heard of the interpolation of Fibroscan scores. You may like to direct your queries to Echosens, the maker of Fibroscan machines.
There are alternatives to Fibroscan to assess liver fibrosis. Platelet counts and FIB4 are good markers.
I am not sure about your interpretations of HBV treatment guidelines. Guidelines do vary and change quite frequently. The trend is towards "treat in all cases with non-zero hbvdna" , but there are still conservative approaches. To interpret the guidelines correctly, you must know the phases of the HBV life cycle - Immune Tolerant, Immune Active, Immune Control, and Immune Escape.
For patients in the Immune Tolerant phase: HBeAg positive, very high hbvdna, ALT normal, and Fibrosis stage 30 years, family history of HCC, and whether true Immune tolerance.
For patients in the Immune Control phase - HBeAg negative, hbvdna <= 2,000 iu/ml, ALT normal, no treatment is recommended.
Normal ALT is male < 35 IU/L for male, < 25 IU/L for female. N.B. They change too.
So do try to consult a HBV specialist. At least a checkup once a year. For men over 40 years and women over 50 years, twice-yearly checks with ultrasound and AFP for HCC are recommended. There are now very safe and effective treatments for HBV, a complete cure is still some way off, but can keep liver fibrosis from progressing, a reversal of existing fibrosis after long-term treatment is possible.