Oh no - sorry to hear this - it seemed like such good news yesterday!
Only you know what's best for you & Beau, so don't feel pressured one way or another - take your time.
I can definitely identify with you with regards to feeling imprisoned by your dog - I'm only now finally able to start getting out for short periods of time & I sooooooooooooooo know what you mean about stress levels!! Just a bit of info to share with you that might help or might not - I'm not sure if you're able to do what we did, but I'll tell you about our 'little howler' anyway!...(Apologies now, cos it might be a bit of a ramble!!)
Max is 24 weeks old today & since we had him at 9 weeks, he's definitely developed a degree of SA - the breeder was home with him & his siblings & parents all day every day & since we've had him, I've been taking a career break too, so I've been around 24/7. We think this might have kind of created a rod for our own backs in a way but we're not sure.
Anyway, right from the start, he hated being shut in a room away from us - even the puppy gate at the kitchen door when he could clearly see us the other side! He also hated his crate & never went in it during the day & would only sleep in it at night if it was in our bedroom with us - we gave in on this one & to be fair, he was 100% fine immediately & has been ever since - he's now graduated to a normal bed in our room & is perfect at night.
However, days were shaping up to be a battle - he truly hated being shut in the lovingly created puppy-proofed kitchen & would howl, cry, bark, pee, poop, scratch, roll in the wee, etc etc etc - we persevered for a few weeks but it was killing me, REALLY distressing him & driving us both nuts! I was starting to think we'd NEVER be able to leave him for more than 10 minutes as either he or I would have a heart attack, never mind the poor neighbours!! I was at my wits end. We tried using a puppy gate, closing the proper door, crating him, uncrating him, using all manner of beds & bedding, kongs, toys, chews, treats, radio, telly, DAP, etc etc etc - argh!!!!!!
He was doing so well with everything else - perfect at nights, 100% toilet trained, good out on walks, grasping all his training, etc etc - in fact, a real joy to have & a lovely, happy, playful, affectionate little character - BUT for the leaving him thing - he HAD to be able to at least see us at all times - preferably be as close to us as possible - the only time he was away from us was of HIS choosing & then only the garden or kitchen for some grub usually! He'd sit outside the loo door & howl pitifully!!
Then, we bit the bullet one day a month or so ago & decided that maybe he had a problem with the kitchen & the closed door - we figured he'd begun to associate the kitchen as the 'evil room!' where he only ever spent any time when he was getting shut in & we were leaving him - otherwise, he was always in the lounge with us & used to sleep in there on the floor & play with his toys in there etc etc etc.
So, we got the puppy gate out again & put it up at the doorway of the lounge/hall & opened the lounge/kitchen door & gave him the run of the 2 rooms - we puppy proofed the lounge as best we could & just gritted our teeth & tried it.
Well, I swear, it was like someone had flicked a switch in him - what a different dog!!!!
I gradually tried leaving him for 10 mins (easy - oh my god!!) then building up to longer etc & in the space of a few weeks, I've got him up to 2 hours, which doesn't sound a lot, but for him/us it's a ruddy miracle & we're over the moon - there is FINALLY light at the end of the tunnel!! I've spied on him & recorded him & even used a webcam to film him (hubby works in IT - men & their toys!!) & he doesn't make a sound - oh my god - I was truly gobsmacked!!
He watches me go, huffs a bit, then either gets on his beanbag or the sofa (yes, I know, the sofa - small price to pay though we figured!) & goes to sleep!! He does wander round a bit sometimes & look out of the window for me & lie by the puppygate a bit, but he's not in the least distressed, doesn't chew ANYTHING, doesn't pee, doesn't make a sound, etc etc etc - I was stunned! We leave him all the usual treats & toys & always tell him 'back in a minute - wait there - good boy' in a happy voice & that seems to work!
Now, I'm not naive enough to think that he's never gonna chew anything or break anything maybe, but so far so good - it's been over a month now. He's so much more relaxed - he still doesn't like me going & he's still exhibiting signs of separation anxiety to a degree, but it's noticeably better than it was - he'll often wander round the house & fall asleep in a room that I'm NOT in for example - BIG development! He also only whimpers now when we're in the loo!! He still hates closed doors though - big time - really don't know why.
Is there any way you could try Beau out of his crate? Is there a room he feels very at ease in that you could maybe pen off an area or puppy-proof it somehow? When you nipped to the Post Office the other day & he was quiet, was he in or out of his crate? I might be completely talking out of my @rse but all I can say is that fingers crossed it seems to have worked for us - SO FAR.
Sorry for the long ramble & if it's all useless info, but I really hope you can find a solution so that you can keep Beau.
Let us know how it goes!
Good luck!