When you have the DMA speed sorted out, set the mode to "Auto" in the CMOS/BIOS. If I remember correctly, Windows should detect it and automatically tick the box.
For parallel port questions, there are good sites such as
Parallel Port Central at
Lake View Research. Hewlett Packard helped develop the ECP specification, but I am told that there is an issue with the parallel driver in Windows 95 which fixes it in "4-bit mode"; I do not know when it was fixed. Read the specialist sites.
Your other questions I can't really answer for sure. Intermittent errors like this could be RAM problems, maybe the RAM settings are too fast.