I use size 4 bold 3 on bookerly. What font I use determines what size and how bold I need.
Distance? Not sure. It would be always the same as I have to look through my bifocals. I don't have much in between vision as I am far sighted. So bifocal for reading and rest for TV and driving. The rest is a blur
Its probably about 1.5 feet or so. I haven't measured. Its why I don't read much sitting on a table on a stand as I have to lean forward to get it sharp through the bifocals and that hurts my neck and back after a while. Talk about slouching.