Hey, welcome!
Firstly I'll say I don't trade 1 Min ORB in the current market generally speaking. The open is quite choppy a lot of the time at the moment. However:
1) Yes eyeball/experience, it won't be the same for something $5 vs $200 for example so can't say exact amount. Different stocks move different amount even considering price range so has to be experience IMO.
2) Yes for the 1 Min ORB it's the range of the 1st minute candle, another popular strategy is the 5 min ORB which would be the first 5 min candle. That's not to say you can't develop your own 2 Min ORB, just not what is taught here.
3) Yes engulfing candles can be a strategy as you might trap some people short or ride along with people buying the dip but bear in mind it's a momentum strategy so I would record that in your testing and see how it alters your success. In this scenario I'd more likely be trading the Fallen Angel strategy (Brian) for a better entry.
4) Depending on the direction of your 1 Min ORB. On a ORB long a bottom wick is fine as this is buying from the lows (bullish) but an upper wick would be bad as there's some selling. Obviously vice versa if you are taking ORB short.
5) Yes taking too extended from VWAP makes risk:reward more challenging. Experience again I'm afraid.
6) You don't, 1 trade at that time. Experienced traders might take more later on but at the open would be asking for trouble.
Martin