Filter problems and Heater Problems

[Allie]

1.We have a Pentair FNS plus filter system that has been using diatomaceous earth for years..We replaced the diatomaceous earth with Fiber Clear and all of a sudden the pressure is significantly higher than normal. Should we go back to using diatomaceous earth?..We were told that diotomaceous earth is carcinogenic which is why we changed to Fiber Clear. We were also told that Fiber Clear is more effective and filters more efficiently. Can we damage the system by changing the filtering chemicals? Is higher pressure bad for the system? Any recommendations?
2. We purchased a blue rubber backwash hose with a clamp to run approx. 30 feet to the closest drain when we backwash the waste water out, however the pressure is so great, the waste water spurts out all over the end of the hose and into my face..Any recommendations? We prefer not to backwash near the filtering system because there is not a drain there. There is also a shed with a wooden floor in which the waste water runs under causing a potential for "dry rot!"
3. Our heater is an old Anthony which the pilot will not stay on and is not energy efficient, so we decided to purchase a Hayward heater. The Pool company installer came out to do a "site inspection". He stated that this particular Hayward heater, when installed will point in the direction of the pool, thus emitting gas fumes towards the pool. I do not want to smell gas fumes when swimming! He stated that this is the only way that this design of the Hayward can be installed. He tried to sell us a more expensive heater made by Pentair, that he claimed when installed will point away in the opposite direction from the pool. Is this true, or is he trying to sell us the more expensive heater? Any recommendations?
4. Also, initially, the swimming pool on site inspector recommended we would need a 250,000 BTU heater to run both the swimming pool and the hot tub, then he changed his recommendations and said that the 250,000 BTU heater would only accommodate the hot tub exclusively and not the swimming pool. He further stated to heat the entire pool in conjunction to heating the hot tub, we would need a 400,000 BTU heater. He surveyed the gas meter and he therefore stated that we needed to phone our gas & electric company to put in a work order for "new construction" so that we could have larger gas lines and an upgraded gas meter installed to be able to run a 400,000 BTU swimming pool heater, otherwise if we keep our same gas meter and not upgrade, then we would not be able to run all our gas appliances in the house at the same time when running out swimming pool heater. Can we get by with a 250,000 BTU heater to run both. Our swimming pool and hot tub are not that big and not that deep! Any recommendations?
Thank You!