Right, so reading all your posts back, this is how it looks to me:
He has a friend who lives 3 doors down from his mum, who also works with him, and for his uncle.
It seems you had a good idea all along that he was with this friend the whole time.
He was seen running past his mums house at 11 the following day with a group of lads so it seems glaringly obvious that he was with the friend who had drugs an perhaps he didn't want his mum to see him. His mum assumed he was 'up to no good'
You know the friend bought drugs on Friday. (The obvious question is how/why did you know this, and given you did know this, surely your first REAL instinct would that that was what your fiancé was doing this whole time, given you are now admitting it's happened before and every three months he has 'blowouts'?)
And you know he was with the friend on sat morning acting suspiciously. I can only guess he was running past his mums because he didn't want her to see him and either realise what he was up to, or tell you where he was.
The uncle has managed to confirm that he was with the work mate who bought drugs for all if not most of Sunday and they then went off somewhere else together. And now he's presumably not able to turn up for work today either, or at least he has no intention of coming home first.
You now seem to be angry rather than worried for his safety and yet in spite of all the evidence you are still reluctant to call of the wedding and admit that you are backing a total loser here.
When you actually read all of that back, what is starting to see quite clear to me is that deep down you knew along that it was 99.99% likely that he was on a drink and drugs bender of his own choosing as opposed to sitting by the river contemplating suicide, or in A&E after an accident.
You are totally and utterly in denial about who and what this young man is. You have your fingers stuck firmly in your ears shouting la la la while you ignore the obvious, go merrily about planning a wedding nd prefer to spend your emotional energies on worrying that the poor lamb might be hurt or in the grip of a depressive episode while runs around behaving like an overgrown teenager without a care in the world.
Meanwhile, you are stressing about money he's spent on booze and drugs that could have been spent on your wedding. 
We'll never mind that, he should be fixing his fucking van, so he doesn't have to deprive you of your car for weeks on end.
How much more enabling of this TOTAL CHILD are you going to do? Seriously, pull yourself together.