Taikor, very long la.

It looks more like a factory than a house from the massive connection!

Most of your question is already covered by ceo684. I think that is enough for you and not to confuse with too many answers.

Rewiring and DB change after the meter is out of TNB cover. Unless you want to relocate the meter. But I guess the meter is beside the gate?

1st, need to come out with the new electrical plan by the electrician. Without the plan, it is a crazy, unorganized, and cost runaway job. Beware that RM6.5k cost is a bit too low for KL/Selangor area.

2nd, identify which area is using a lot of electrical. Living room, 2nd floor or kitchen area. Is the kitchen has a lot of appliances like oven microwave, induction cooker, WM, fridge etc. For example, if the 2nd floor has a lot of AC, heater, PC etc, so it is better to have another DB separated. Or the kitchen is far behind and with plenty of high current running appliances.

3rd do not neglect the earth and lightning. Plunge more earth rods into the ground and run the earth wire separately to DB. You don't want headache later when RCD keeps on kicking.

The bolts rust is only the surface. If knock on it and it doesn't brittly break, that is fine.

If want to change the tiles + gutter, might as well change the wood trust to metal. Consider termite also.

The ground rod is normally locate at the garden. If the front yard is tile up whole place, than the tile already cover over it.

The earth wire lay directly to the DB. Doesn’t go through the meter side.

Lay another ground rod help reduce the lightning trip.

The earth wire from the 2nd rod not necessary to be joint to the DB. Can wire up to any wall socket or joint to any existing earth wire.

You can get a new DB (smaller) to house the SPD. Than earth wire to existing. Or new ground rod side.