The easy part first... tobacco is not a violation of the precepts.
OK... for the fifth precept..
Suramerayamajjapamadatthana veramani sikkhapadam samadiyami:
I observe the precept of abstaining from intoxicants that cloud the mind and cause carelessness.
Sorry, but that translation is not good enough.
The best way of translating this sentence, is to start from the end.
samadiyami = I undertake
sikkhapadam = the training precept
veramani = of abstaining from
Now for the long compound:
This is a compound made up from sura + meraya + majja + pamada + thana
sura and meraya are two different alcoholic drinks. Sura may be a kind of beer, and meraya maybe some kind of cider. Anyway, both are alcoholic.
majja = either intoxication or intoxicant drink
pamada = indolence, carelessness, negligence, intoxication
majja and pamada are practically synonyms here
now for the last member of the compound: thana. This word means "condition".
So, suramerayamajjappamadatthana is literally "beer-cider-carelessness-intoxication-condition".
In order to make this into a more idiomatic English, we have to start from the end: "the condition of intoxication and carelessness caused by beer and cider"
So what then does the precept say? It says: I undertake the training precept of abstaining from the condition of intoxication and carelessness caused by beer and cider (or, alcoholic drinks).
This is the literal meaning of the precept. Not to abstain from the drinks, but to abstain from the condition of intoxication.
You may say that as soon as you drink, you will get intoxicated, so that the wise thing is to abstain from the drinks in order to abstain from intoxication. I fully agree on this point. The sensible thing is not to get drunk, and in order not to get drunk it is wise not to drink.
But if you know yourself so well that you know that you can take a small glass of wine or beer without getting drunk - and stop there! - the precept is definitely not broken.