Hi all, I am alternating between utter depression and vigorous hope every few hours now after one of our cats, Starsky, has been missing for 4 days now.

Here is a link to my post in the Lost section of the catchat forum:
http://www.catchat.org/discus/messages/7/65313.html?1198224594I have a few concerns and questions and would value your thoughts please. I have taken time of work and been looking and postering almost non stop since he didnt come home the first evening.
We live on the corner of a very busy 4 lane main road and another pretty busy 2 lane road. Our garden is walled in and the back faces onto some other large gardens. We keeps our two guys in each evening and night and they are free to come and go during the day via a catflap.
Our missing cat would always have come home throughout the day for naps, especially now it is getting cold. He would not have walked on the footpath, let alone crossed the road, as far as i know..(which is part of my question ill come to)
He is neutered, cautious and intelligent. He wouldn't sit about for someone else to lift him.
Q.1 I heard that David Attenborough said that they tracked a normal domestic cat 12 miles in one day...when its owners thought it just wandered locally... is this "normal"?
I have been searching and posting leaflets in each house where i was pretty sure he would have roamed (very close - about 5/6 houses distance) and also searching beyond that to the end of the streets and those parallel. If however, he potentially could be going miles....I am screwed and can never explore all parts so far since i live in a densely populated part of the city...
Q.2 I have had one sighting reported of him the night after he went missing... of him looking ok..BUT..he was only about 120 meters away from where we live...and he was walking away from our house direction...?
I have shown the person (who says he spotted him) other pics and he is quite sure it was him. I am stumped.. why would our cat, who is soo loving and loved, suddenly for no apparent reason (he is not one who normally does this at all in his 3 years of life or 1 year of living there) do that?
I have stayed out, watching in case i could see this cat to confirm if it was him or not; one night from 6pm-3.30am and the next morning from 6am-8am. I saw a fox and one other black and white cat, but not my guy.
The spotter is a cat lover and observer, so i dont doubt his sincerity, but it just makes no sense to me and is confusing how i should spend my time searching for him - keep looking very locally? or go further out?
Q.3 Does a cat look out for cars before crossing a road (like some dogs know to do) or do they just sprint and it is pot luck?
Q.4 If a cat did cross a road which was quiet at the time, maybe if they were chased for example, but then the road became very busy - would the cat, who was now in unfamiliar territory, still "know" where it's home was and be able to get back via a new route?
(There has been building work next door to us recently which potentially could make him think his way is blocked (though he could sneak past at the back hedge), however i know building work would be very disruptive to him.
Q.5 How well do cats withstand the cold?
He is shorthaired and slim. It has been VERY cold here, down to 1oC at nights as i know because i was out in it for hours on end.
Q.6 Is hiring a trained tracker dog to try and find our cat a feasible and realistic idea or not? Their may be one organisation in my country to do this.. I was told by another that this is usually for humans (obviously) but i wonder if anyone knows of it being done and successfully for cats?
Thank you very very much for reading all this and if you can answer one or more questions i would be so thankful.
Tim and Starsky's family