Andreas it is a little hard since you are unsure of the yield (quantity of water you well will give you), however from the information you have.
Well is 152 m (500') deep.
Standing water level is 30m (100').
Here in Australia blue line poly is rated for 120m head, I prefer and use poly for small submersable pumps.
So 120m is 400 feet in round figures, so with your day tank 3m (10') above ground if you used poly of this rating you could saftley set your pump at 117 m. So this gives you 87 m of water over the pump, so lets say you set your probes to pump 80M of water leaving the pump with 7m of submergance, a good safety margin.
When I set small pumps ( 4" subies) at depth I prefer to use two stainless steel safety cables, I use a stainless steel female union above the pump that has had two oposing lugs welded on, to this the safety cables are attached.
I asume your well is a minimum of 4" (100mm) so
for 80m so 3.14X 0.1x 80 = 25 m cubed of water, per cycle of bore. Now thats a lot of water.
Now crushing is not going to happen, for there to be a crushing force on the rising pipe it would have to be empty with the well full, this does not happen. Crushing force could be a concideration for the well liner but I must assume it has been professionally done therefore has adequate casing strength.
Flexable rising columbs are easy to pull up, you set up a pully ( wheel rim is good) about 1m above and to one side of the bore, them pull via the safety cable (stainless steel cable).
In sumary I would use 1 1/2 polr of suitabe rating setting the pump as described.
If you had the need to set the pump lower you could just join in a higher pressure rated poly between pump and "existing" pipe. The higher pressure is at the lower end, a poly pipe can burst if a submersable pump is run against a closed head (ie a shut valve) so best to have the outlet open and control with level probes.
A bit long winded I know but hope it makes some sence.
allan down under