CareerCup

It does, you get less data rate because wifi ack-s round-trip time increase.

Data rate reduces as the distance increases because
a) Interference increases with distance
b) Higher interference causes higher BER (Bit Error Rates)

In cell phones, as distance increases mobile will transmit at higher power to offset the interference. Where as in wifi, there is no advanced power management.

It doesn't.

I don't think so, only the first packet's delay may be higher(with increase in distance) due to higher propagation delay. Remaining packets will only have transmission delay, because its propagation delay is subsumed by the first one.

Also acks should not be taking more time, if piggybacking is done or any window protocols are employed effectively(appropriate window size and time_out).