Borewell low yield & pumping issues in Bangalore, Karnataka - Need advice

I have drilled a borewell in Airport Road area Bangalore. On drilling I came to know that the area is quite rocky. The details regarding the borewell are as below.

Bore Drilled : 6 inch
Depth          : 612 feet
silt at bottom : 25 feet
pump           : 2 HP Air compressor
water pipe     : 500 feet
Water stream : 1
stream depth : 350 feet
static water level : 125 feet from gound ( after 2 weeks from drilling )
Yield promissed by driller : 0.75 inch

Method used : surveyed by geologist with meter
Yield promised by geologist: 1.5 - 2 inch

There are a few borewells in the region giving yields ranging 1 inch to 3 inch in summer, when I put the motor for first time I got water at the rate of 300 liters per 20 mins. Later after 2 - 3 days it has gone down to 300 litres per one hour, later to 300 litres per day. Reduction in water has resulted in the same being available only in the mornings. The pump technician indicates that we have a 50% per more chance to get more water here.

As I mentioned above there is a 50 feet gap from silt level to my water pipe level.

My questions are:

1. Can I extend the pipe till Silt level ?
2. For Air compressor pump is there any problem if it touches the silt level ?
3. Will I get more water given the situations above if i extend the pipe ?
4. When to start motor during a day so that I will get more water ?
5. Will the 2 HP pump suffice to pump for 550 feet ?
6. Is there any possibility to check any other bore is drawing water /sharing the same aquifer?

Chandra Sekhar Vakada