1. This one is tough. I am not sure if we can defeat 6♠ more than one trick, so I could see myself passing here, of course bidding 6♣ over 5♠. For them it should be easy to spot the big double fit and bid on. Against very conservative or weaker opponents I will bid 6♣ and hope they let me play there. 2.4♠ Anything else would be ridiculous. 3.Very close, with the 10 of ♠ I would certainly X. There is a good chance that ♠lead is the only one to beat it. I don't think they will ever redouble me, -180 is not the end of the world...... With my actual holding I really dont know, I have support for any suit my partner leads...