The 'alternate reality', pre-financial scandal meltdown, when it was touted that 50% was more than possible, and in that event, Independence negotiations would begin. At the time (again pre-financial shenanigans), Humza was also being floated as a likely replacement for NS
As far as what will he do 'if' they win 29 plus seats and Westminster says 'no', it just rolls on to the next Hollyrood election doesn't it..and then presumably to the next GE after that.
The question with the latest 'strategy' is..why is Holyrood regarded as a 'de-facto' Ref, but the GE isn't? Neither of course are.