Path loss effect on BER
Generally speaking, the BER only depends on the SNR. If the received signal power $P_\mathrm{S}$ is reduced due to path loss, while the noise power $P_\mathrm{N}$ remains constant, then the SNR will be reduced, because the SNR is defined as
$$
\gamma = \frac{P_\mathrm{S}}{P_\mathrm{N}}
$$
Consequently, the BER will be increased and the answer to your first question is: yes. However, this should not influence your BER vs SNR curves. Thus the answer to your second question is: no.

If your simulation behaves differently, i.e. if introducing a path loss "shifts" your BER curves, then the SNR is probably not calculated correctly. I suggest that you estimate the received signal power $\hat P_\mathrm{S}$ at the receiver (just before the sampler). Then the power of the additive noise should be calculated by
$$
P_\mathrm{N}=\frac{\hat P_\mathrm{S}}{\gamma}.
$$
Then add noise with mean power $P_\mathrm{N}$ to the received signal. With this setup, your BER/SNR curves should be independent of path loss.