1. In flight. Do you have FAs on board? If so, let them deal with it as per SOPs but start checking for suitable divert airfields.
If not, if you're the FO, chances are you'll be the one dealing with him/her. If there's SOPs dealing with it, follow them. If not, keep out of range of fists and feet, explain firmly but calmly that the behaviour is unacceptable and if it continues, you'll be diverting and met by the police. If it is possible, find out why he/she's kicked off. Drunk? Kid kicking the back of the seat? etc. If the source of the anger can be found, sort that out.
2. On the ground. Similar to above. Find out the source of the aggravation. If the behaviour escalates in spite of intervention, get the police over and kick him/her off the aircraft.
3. Smoke. You can't feel it. You can smell it or see it. Question further, e.g. air conditioning systems in a humid environment will blow mist. If you're downwind from engines etc, their exhaust can be introduced into the cabin, likewise a downwind start. (via the APU). If so, that's normal and the captain is correct.
Any other situation, you would need to press further your concerns.
4. Touchy one this. Have a look at his/her appearance. If you are sure that someone did spill stuff on him/her, suggest a quick change to ease suspicious security guards. If you are pretty certain it is a drink issue, suggest that the captain goes sick, you could cite that if you could smell it, then security will smell it and will report you. Etc.