Does alcohol intoxication raise the seizure threshold since its a sedative or no? Also can it prevent convulsions like other sedatives?

In high amounts. will lower the threshold making you more prone to a seizure, Acute alcohol withdralwal wiil icrease seizures.
Not intoxicated. The dosage that might be okay would not cause intoxification - it would be very low. Here's info: http://www.epilepsymatters.com/english/lwealcohol.html As it says, if the seizures are not already under good control - it is risky and may bring on a seizure. I'd avoid more than a few sips - small glass of wine w/ food in any case. Talk to your own doctor too. You are special.
Seizure threshold. Alcohol in small amounts (less than 2-3/day) usually will not raise your seizure threshold. More alcohol than that can raise it. Best to stay away from it altogether unless you have alcoholism the withdrawal from which will almost certainly cause seizures to increase.