1. I don't know anything about ITOM bikes that new, It's possible its a re-badge, which was very common on bikes like that.
2. Oil is mixed with the fuel, a 40:1-50:1 ratio would probably be about right.
3. Get the seller to fill out a bill of sale, you want this at the very least.
4. They may be the original tires, It may be best to replace them before you put too many miles on the bike. Replacement tires are inexpensive.
Here is a little info.
1973 - Itom ceases production of their own engines and adopt Franco Morini engines for the whole range. Itom is no longer a real manufacturer, but more an assembler of motorcycles.
1973 - New range presented in December at the Milan Motor Show includes two 125cc models. one a street-scrambler with F.Morini engine, the other named Cross Competition with a Zundapp unit, but both remain prototypes. All 50 production models now have Franco Morini engines.
1975 - End of production: The venture into medical compressors and water-heaters was a financial disaster and the losses led to the closure of the motorcycle division.
Here is a bike like yours that claims to be a 1976