Hi hun, looking at your routine I would guess he is overtired, a 14 hour day with 1.5 hour nap is very long for an 18mo. Can you get him in bed earlier, say 6.30/7pm so at least he gets more like an 11 hour night?
Do you wake him from his nap or does he natrually wake at 1.5 hours? Again 6 hours from wake til nap seems quite a long time.
Also he could very well be teething, do you medicate before bed? And have you ever tried giving him meds whilst he is asleep? (like a dreamfeed) Lots of mums find this works well for early wakings.
xxx