"what i am asking again is how many votes of No or Yes does it take to either bring it down or see it through.
is it 51 percent and over for a No Deal?"
As explained, half those voting plus one will decide the vote. However, it is not "51 percent and over for a No Deal?". The vote is to accept or reject the deal on offer. If it is rejected it is very unlikely the country will leave with no deal. Neither the Westminster Parliament nor for that matter, and often overlooked, the EU, has the stomach for a No Deal departure. The EU will move heaven and earth to keep us captive in its customs union to prevent us striking beneficial deals elsewhere. Meanwhile many people in this country have been scared witless by preposterous "scenarios" and forecasts promulgated by the likes of Mark Carney and Philip Hammond which are based on totally unrealistic assumptions and which stand less than no chance of being fulfilled. So moves will follow to either delay our departure or organise a fudge which means we either do not leave in March or "leave" under some sort of "stalling" agreement.
The EU will not agree to anything which sees the UK able to gain an advantage over its remaining members (that's what the leaving "agreement" is solely concerned with). That's why a "no deal" exit is the only one which will see the advantages of Brexit realised. Whilst it is the exit which will see UK businesses and politicians put to the most trouble (much of which could have been allayed had they begun preparing for it two years ago) it is also the exit which will see the UK gain the most advantage from our departure. One thing's for sure - remaining imprisoned in the EU's customs union - which Mrs May's deal will see us doing almost in perpetuity - will do us no good at all.