Since the first doctor has informed you about the murmur, you will not be able to allay your anxiety
till you are absolutely sure of it. So get an ECHO done to rule out any underlying heart problem.
Some children have minor defects in heart which close on their own with time without any treatment. Get his eye check up as he can have a refractive error
Bring down the fever
and get his blood tests done to rule out any infection.
will be able to ascertain the cause of fever and treat him accordingly.