I know how you feel. Luckily I built up my Cervelo myself. I’m sure it weighs at least a kilo heavier than advertised, thanks to all the grease I put everywhere. LOL At least stuff comes apart easily when I work on it.
I had a steel KHS I’d used for commuting for about 8 years. It was in an accident so I got a new bike. Carbon, but not as nice to ride as the steel steed. Anyway, all the bits came off the KHS pretty easily except for the BB. I had the correct BB tool and a long wrench and gave it death. Nuthin’! Bugger. I tried several times over a week, using WD-40, penetrating oil, dishsoap and all sorts of things. Nuthin’ but skinned nuckles. Why all the hard work? I wanted to strip the frame down, bend the slight curve in the downtube back to straight and if possible, turn it into a single speed after a nice paint job.
Well, after just about giving up, my son suggested the air powered rattle gun he has. Eureka moment.
Well, I lay the frame down, put the BB tool onto the impact gun put my ample weight onto it and rattled away until the air tank ran dry. Let it build up pressure and go again. After 45 minutes of on again off again rattling, swearing, lubing and such, it turned about 1/10th of 1 degree and then without warning, spun out completely! Voila, a perfect BB came out and a perfect BB shell was left! Wahoo!
So then I attached the other side 
You guessed it, another 45 minutes of going nuts on it and it too buzzed out leaving both bits perfect! I cleaned up the BB and the shell, and lubed them both. The BB became a donation to a friend building up a bike for the trainer, and my frame got sanded and is awaiting paint.
The BB had been in for 8 years and over 75,000km of summer and winter riding in salt laden sea spray soaked rides, but was still turning smoothly. Gotta love sealed Ultegra BB’s 
A few weeks later I visited a mate as he was building up a P3 (old ali one) and I said lube the hell out of it. He took a Q-Tip and dabbed on a tiny bit of grease and wiped it around with his finger. I bet that BB never comes out…ever! (Dissimilar metals will sieze together faster than the lips of two 17 year olds at a school dance!)
(it sounded from your post that you put the old headset bearings back in? WTF? 