It's possible - and I can't say anything more than that without seeing pooch in action so to speak - that he's basically telling you to feck off because you're asking him to do something he doesn't want to do. Most dogs don't think much of doing anything which doesn't benefit them. There is no reward or purpose in coming indoors but there is a purpose and a reward in barking... it scares all the would-be nasties away. So, you telling him to get indoors produces the canine equivilant of "Feck off, why should I!".
The trick is not to force him into obeying by raising the voice or dragging him in (especially not the latter) but to make it worth his while. So, next time go out there with his very favourite toy or, as he's a goldie, better still his favourite, smelliest food treat all call him to you. Praise him when he gets to you, tell him to sit and offer him a treat when he does. Then, with another treat within sight and smell range, command him to go indoors using whatever word you normally do. You may find he goes without question, in which case follow him IMMEDIATELY and just as fast shut the garden door and give him the reward. If he doesn't go of his own accord, call him to follow you in by showing him the treat and then give it to him IMMEDIATELY he is in and the door shut. And as ever with dogs, repeat, repeat, repeat consistantly. You may like to use the clicker in this - I don't so can't comment on how to integrate it with my own way of doing things but if pooch is clicker trained already I'm sure that will make it easer for you both.
I'm no trainer, I rescue, all I can say here is that the above has worked for me with several dogs (my own, foster ones and those in rescue) and with others I know too but when in doubt refer to/back to a qualified trainer who uses reward based methods.
If the crouching is of the paws outstretched on the ground, bum in the air variety then he's inviting you to play - but still training him to come in upon instant command is worth instilling in him.
The problem you describe is very easy to overcome but it DOES take consistancy. Make sure both you AND DH/DP use the same method of training him to come in EVERY time, no matter how busy you are, and whilst training him do NOT let children let/call him back in.
Don't give up, they drive you nuts sometimes, dogs do (I know, I have 3 big uns!) but a little time invested now will bring huge rewards for years to come. Again, if in any doubt, get straight on to a reputable trainer or behaviourist. He's coming up to teen years, this is the hardest part of owning a dog from the POV of behaviour and the age at which so many are dumped in rescue... and if only those owners had nipped problems in the bud with consistant training rescue would be a lot less busy and I'd shed a lot less tears.