I agree with what others have said - scruffing is not something I would recommend - it's not what the mother would do, and it is a hangover from the old dominance theory advice that sadly a lot of people still give out. But I don't blame you at all for resorting to it - you are obviously putting in so much work with Ollie and without the support of your family that must be absolutely exhausting - Ollie is at the age where most puppy owners are tearing their hair out - Honey had me in tears on several occassions at around that age, and we reacted in frustration at times - but it is better to be proactive and prevent the problems is you can.
A "leave" command is something you can teach, but in the meantime everyone needs to keep Ollie away from situations where he might do something that is not acceptable...
Looking at what you described (and with the benefit of not being in the situation) I think I would have run away making excited noises, or used a squeaky toy, to distract him from chewing - if he hasn't yet learned what "leave" means, don't set him up to fail by telling him to leave something he finds rewarding. Personally I wouldn't recommend a water pistol either, as this can backfire and cause negative associations with something else completely...
(Oh, and I have acted like an absolute loon on several occassions simply to regain control of Honey - the best one has to be at one of our first older puppy romps when all the pups were merrily playing and we were asked to get our pups back and play with them instead of them playing with each other - Honey was far too engrossed in playing to pay any attention to our calls, treats or toys, so I squealed her name in a really high pitched voice, and rolled around on the (muddy) floor with my arms and legs waving all over the place - Honey came to see what on earth I was doing....
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I think Ollie has learned that running off into the garden with stuff is a good way of getting attention (especially if this gets him attention from people other than you??) - as long as it is something (ideally a treat) that isn't the end of the world, call his bluff and run away inside and be really, really interested in something else in there (get down on the floor and stare at it) - he'll soon come to investigate what is so much more interesting than him!! But keep that up - don't let him see whatever it is you are looking at - you need him to think it's really really good - this should help encourage him to drop whatever it is he has. Once he has dropped his treasure, give him the treat, but make sure you can get his treasure back (lure him away from the treasure using the treat, maybe?). Honey learned that she could get a great game of chase out of us by taking the laundry off the airer - after a while we cottoned on to this and, as she never damaged or ate the socks, we decided to ignore her efforts - she pulled about 15 socks off the airer, and put them all in a pile nearby, barking desperately trying to get us to see, but she eventually gave up!!!!
Good luck - I hope your family begin to see just how much you are investing in Ollie, and how much more difficult this is without their co-operation....
