I hear ya on USPS issues. I've had a rough time with them lately too. They destroyed a well packaged box and lost one of the books from it. The customer was disappointed and I had to send another book as a peace offering, but it wasn't a direct replacement. Priority packages don't seem to get as badly treated. I think they go to a different sorting center. Unfortunately, the shipping cost is high.

FedEx is the way to go for me on heavier items. They haven't lost or seriously damaged anything yet. I can pay extra for pick up or drive 25 miles to the nearest drop off point so I have to watch my costs.
The only problem with the signature required is people who live out in the country like me and are at work when the FedEx truck runs. If I miss it, I have to make a 50 mile round trip to get my package. I try to not make my customers go through that.

Hope you get rid of that sinus infection, not fun.