Brian, K6STI, has some nice mods on his site, ref'ed elsewhere in this thread, including a fix for (2). He's also modified that site to include some alternate procedures for flattening the treble roll-off problem by adding some feedback capacitance (vice removing some smallish surface mounts).
I've been investigating retrofitting a digital output - may have some news about this in the future. I wish Sony would put out a no-holds-barred tuner, based on this design, that incorporates digital outs and fixes all the warts, but I suspect they've (rightly?) concluded HD Radio is limited in terms of ROI.