To address your last point first. When it comes to drink driving, absolutely I am without sin.
There is already a sliding scale of punishment. From being just above a relatively high limit in the UK (with 14% tolerance above that limit) incurring a minimum 12 month ban right up to imprisonment for being many times over and for repeat offenders.
Your idea of punishment based upon time and location sounds fine in principle but is widely open to interpretation and the only winners would be drink drive solicitors eager to pull in the punters with the offer of a chance of getting off subject to paying a princely sum. Win or lose for the charged drink driver, the solicitor always wins.
I'd be interested to know where you get your stat's from around the inflation of drink drive accident figures. Surely, the decision to drive or not is made before you pick up your keys in your house, not when you are sat outside in the driver's seat. At that stage you are going to drive. If someone runs into the back of you and you are arrested for being over the limit maybe it's a blessing because you didn't get the chance to drive off and pile into some innocent unfortunate and either kill them or put them in a wheelchair for the rest of their lives.
I'm sure that those who consider themselves 'unlucky' to be caught the morning after are not as unlucky as those whose kid gets mown down on their way to school by someone incapable of making a simple units calculation. To allow for metabolic uncertainty, just add 25% to the time you 'think' you are at 0. It's not rocket science. If you are in any way unsure. Get the bus or walk.
You accept that accident numbers will reduce if the law comes down hard on all offenders. Isn't it worth saving lives for the sake of inconveniencing poor decision makers with a ban?
Again, the assumption that everybody, over the drink drive limit, will cause an accident. The assumption that everybody KNOWS how their body will deal with alcohol, every day ( which sadly differs for everyone, every day ).
All you do is take the worst case scenario and apply it to everybody.
There are bad drivers out there, the sort that have caused many accidents but rarely get involved in any. Lets shoot them too.
Speeding causes accidents, tiredness causes accidents, badly maintained cars cause accidents. Shall we shoot them as well.
After all, according to you, it will save lives.
The accepted 'layman's' term for a safe level of drinking and driving is 2 pints, not accurate I know but nothing is in drink driving. Even the 'accurate' breathalyzer at the police station is different each time you get measured So, 2 pints roughly equates to a reading of 35, therefore a reading of 43 is roughly about 2 1/2 pints or 3 depending on time taken to drink them, whether you have eaten, whether you are tired, how often you drink, body fat content, time of day, time of month, etc etc. Even the police don't prosecute on readings below 40 ! Yet still, nobody can say, with any reasonable amount of certainty, how much will actually put you over the limit.
The habitual drink drivers need sorting out, most pubs will tell you who they are. But the first time offenders, the ones that took a chance because of the absolute uncertainty of whether they are over or not, should not be tarred and feathered by people like you because they did not know if 2 pints or 2 1/2 pints would be enough to put them over. You will no doubt shout, with the high moral ground, that if you are unsure then you shouldn't drive. it's time to start living in the real world, people take chances every day, in all aspects of life.
I agree with you, those that know, for sure, that they are too drunk to drive should be shot.
Those that thought that they were ok, but mistakenly were not and just failed, perhaps shooting them would be a bit excessive. Having read your posts though, you will probably disagree.