i) A time interval program, so you need a real-time clock. I built the one described in the tutorial. I had errors too which I corrected and so got my own program (more or less heheh). After this clock it's just a matter of an if-then else to switch the relays.
ii)The voltages you measure are converted to bytes by the internal A/D converter of the 80c535. My guess is to use a binairy to bcd converter to express that in degrees (software indeed). See the code library.
iii) To control the relays you need to know whether they are AC (use triacs or opto-triacs) or DC (use ULN2803 or opto-coupplers.

Do you want to display the results/time etc? LCD, LED? By port-pin or ext.device?