After going through history of your father,he is diabetic and hypertensive and developed a stroke
and after treatment he has improved significantly, as blood supply to pons area was affected hence he has balance problem called ataxia.
He is already receiving correct treatment,which consist of anti platelets,neuroprotective agents, anti hypertensive drugs and good control of diabetes
Initially there is some delay in starting proper treatment but as he responded well to treatment he should continue to improve.
As he is already recovering good physiotherapy
will help him.
There is no need to repeat MRI
,he should continue to take therapy and physiotherapy.
In stroke improvement is slow just take good care and physiotherapy, periodic check up with Neurologist