Re #4: When an airline joins ST, they typically keep their own Frequent Flyer Programme, in which case it will not be possible to merge the account with an FB account. Only smaller airlines sometimes choose to adopt one of the Frequent Flyer Programmes of a large ST member (but this does not mean that this programme is FB!), in which case accounts will be merged. I cannot see any reason why any Indian airline would decide to use FB as their programme. So your strategy of hoping for a merger of accounts is very unlikely to work.

In your case, Supersonic Swinger's suggestion is the only one that makes sense. (But note you won't get level miles, just award miles, and status perks are likely to be restricted.)