Hello and welcome to healthcare magic!!!
From the symptoms and the history its clear your father is suffering from what is called an ischaemic stroke
and depending on the artery
involved and the extent of the infarction
your father may take time for recovery, i would ask you to be optimistic but with caution considering his age and pacemaker status he will recover slowly and with proper physiotherapy
and treatment should be getting better as soon as possible the treating neurologist
will be in a better state to tell you the exact time but since you say infarct is left sided the right sided limbs will be more affected so dont lose hope it will take time but he should get better soon.