Connecting headphone and tablet to high end system

Whoops, perhaps your tablet is not an iPad. I do believe you can get digital out into a USB form on other tablets too. That is worth researching.

Yes, you definitely can use the tape inputs and outputs for that purpose. However, you may want to consider using a better adapter to get digital out of your tablet and sending it to a DAC, rather than using the headphone out of your iPad. If you have a newer iPad, you can get a lightning to USB adapter and feed it into one of many USB DACs. As for the headphone output, the possibilities are limitless regarding headphone amplifiers and headphones themselves. There are many headphone amplifiers with RCA inputs such that you could use a standard interconnect to feed the headphone amplifier.