Having read the entire thread from first incoherent ramblings to this mornings slightly more comprehensible utterances - I think I can tell you the problem with your PIL.. It has nothing to do with them not trusting DH.. or friend. It's YOU !!
If I had a daughter in law with the same complete lack of communication , understanding of social pleasantries and brazen entitlement I would not wish to have DH and you in the house alone because it appears you have no boundaries.
You explained in one of your clearer posts that the evening should have gone like this ;
You and DH join PIL for pre drinks before leaving for a venue where you won't have the opportunity to socialise together. So pre drinks would allow you to have some social time with them. ..
However you are 50 minutes late and pre-drinks have finished and PIL are ready to go.
Therefore the correct way to behave is to arrive - offer perfuse apologies, use the loo if needed and follow on to the venue. There is no point in the pre-drinks as it's purpose was to socialise with your PIL and they have gone !! -
It sounds to me that your focus was not to socialise but to drink. I think your PIL know you like to get hammered and the eagerness to get you out of the house was to limit the time you had to down the booze and prevent you from arriving at the venue drunk..
They are from an older generation- so instead of hassling you directly to leave the house - the address their wishes to their son in the hope that him leaving the house would mean you would too.
Have a look at your relationship with alcohol OP.... improving that may also improve your relationship with your PIL.