From the last week's check on the data bus, it looks like there's some resemblance to whatever other dump that comes from this website:
One of the posts mentioned about a dump from another cheap NOAC console:
E000 D8 CLD E001 78 SEI E002 A2 FF LDX #$FF E004 9A TXS E005 A9 00 LDA #$00 E007 8D 00 20 STA $2000 E00A 8D 01 20 STA $2001 E00D A2 02 LDX #$02 E00F AD 02 20 LDA $2002
And here, from the recording of the data bus earlier:
78 D8 A9 00 8D 00 20 8D 01 20 ...
It could be a startup code, and this varies on ROM to another ROM. I'm not familiar with 6502's assembler - I might need to try to have the cheat sheet (6502 instruction set list) ready on my side and read it.
I'm now trying to dump the entire ROM and try to dissect it further. It is not gonna be easy, I admit!