HD Antenna Specs / Distance

Yes, you should have a grounding block wired to a ground rod before the antenna wire enters your home. It won't necessarily prevent all damage from a direct lightning strike, but it will help.

NEC in the States (NFPA 70) says that if you don't ground the grounding box to the same ground rod that is connected to your breaker box, you need a #6 wire between the ground rods. Obviously, that doesn't apply in your locale, but it's still a good idea.

YMMV, but I get excellent digital TV reception from an antenna mounted in my attic. Removes all the worries about grounding, wind, etc.

Grounding the mast is a very good idea if it is metal. You can get ground clamps that are designed for use with water pipes and conduit of practically any diameter. They are two curved pieces of metal that have machine screws on either side to clamp to the pipe. There is also a screw terminal for your ground wire. I would put a separate ground rod in, but bond it with your other grounds at one place.

I would recommend not running the coax over the gutter, or for that matter over any exposed roofing material period, as the cable will be exposed to UV radiation and break down faster, as well as trapping leaves and other foreign matter. I would run the coax cable around under the eaves around the house.

One final thing to mention, is to use outdoor rated cable and connectors as corrosion can be a real issue. Also check your local codes and HOA's to see if they have any restrictions to tall masts mounted on your house.