Finder Internal SD card questions

Hi everyone - I love my Finder - it's my go-to printer for quick & easy prints -
Now I am getting reliable prints - A couple of questions -
1) Do I have access to internal memory from PC (I am using FF software on Linux Mint)
2) I keep getting machine shut down part way through print (I assume it's when I leave USB cable attached - According to forum posts)
3) In last few days I have been deleting old prints from internal memory via touchscreen - But new prints seem to be missing from list if I want to re-print
4) What is the standard capacity of internal SD card & is it worth replacing / upgrading

Thanks in anticipation

Regards

Martin