I read that blocked middle ear/Eustachian tubes can cause nasal congestion as they are connected up to the back of the ear drum, yet flushing these out with salt mixed with water has no effect.
So can ear wax cause restricted breathing ?
In addition to the above, see this diagram. Your MIDDLE ear (highlighted in blue) connects to your sinus via the Eustachian tube (where it drains into the sinus cavity isn't showed). Your EXTERNAL ear canal is where the wax is, and it's separated from middle ear by the ear drum (TM).
Also, many physicians advise not to use cotton tipped applicators in the canal; they tend to just pack wax deeper and cause it to become thicker/harder to remove, and also risk perforating the ear drum.
FYI: It's also actually that nasal congestion and blocked Eustachian tubes can cause middle ear fluid or infections, not really the other way around.
If nasal congestion persists, consider seeing a doctor for evaluation, as it may be allergic rhinitis or various other causes, which can cause middle ear effusions if untreated.
It seems unlikely that ear wax could cause nasal congestion and restricted breathing, since in relatively healthy individuals, the ear canal is separated from the middle ear by the tympanic membrane (aka the ear drum). If the ear infection, or the Q-Tip, or however you "flushed" the middle ear, caused a perforation of the ear drum, lots of things could be going on.