Usually a middle ear infection
i.e Otitis Media
is associated with pus discharge .Wax accumulation would in rare situation lead to ear infection.
However there are few behavioural issues along with speech problem which is of concern.Wax leads to conductive deafness
and hence it would be advisable to get his wax removed and then perform Auditory function test to rule out any other form of deafness.Also he might need a thorough neurological examination to know why he is clumsy.
I would advise you to fix up an appointment with his Paediatrician and ENT specialist
for further evaluation