You're a great place to be at! You're results are great and suggest you will likely lose the surface antigen in the near future. I would consider myself lucky if I were you.
Your dad's doctor is right, since any rise in his viral load was likely due a weakened immune system as a result of infection and antibiotics and not that the virus has mutated. It's great news his fibroscan is so low at his age. He should continue to get monitored in 3 month intervals as the doctor suggests and if the viral load falls back under 2000iu/ml, no treatment will be a indicated and he can get monitored 6 monthly thereafter.
History is as below-----
My father age 61 diagnosed with hep B accidently a year ago .At that time test results were hbseag NEG HBEAB POS hbv dna 242 iu/ml hbsag quantification 300 ast 35 alt 30 afp 2.52mg/ml .fibroscan 3.3kpa.
Doctors adviced no treatment needed and put him on vit b &c .
We checked after 3 mnth again ast/alt came normal within 40.
Meanwhile he contracted hand inffection and took antibiotics for 2 months.
After 6 mnths we tested again and results were not good
Alt 80
Dna load 4lakhs iu/ml.
We went for tests again at ilbs after 8 months and results came back to normal .(antibiotic stopped , on vit b&c)
Ast/alt 25 both
Hbv dna 142 iu/ml lft /kft normal afp 2.6
Not docs told no treatment needed as of now ,alt to be monitored every 3 mnth , lft/kft /dna load /ultra sound to be tested after 6 months.
He told treatment is suggested when either
1)alt is high for a prolonged time
2)fibroscan is more than 8
3) biopsy comes abnormal .
Viral load keeps fluctuating .