Data stream is not ASCII codes, but rather key codes. Key pressed (key down transition) and key released (key up transition) are both sent to computer. Both sets of information can be interpreted by software.
Reference used for the data above: Amiga Hardware Reference Manual, ISBN: 0-201-11077-6, Copyright 1986, Pages 236ff, Appendix H, Appendix E-3.
Verification of pin 1 to 4 with hardware will be done as soon as I unpack my A1000.
Amiga 1000 keyboard connector is not rj11, its rj10.