Routing over 8 MHz crystal traces
R4 and R5 are often included in order to match the impedance of the IC and crystal. My guess is that the two pins of the IC are (for whatever reason) mismatched, and so one side needs this extra impedance to give a good clock signal.

As for the signal traces crossing the crystal traces, it really depends on the strength of the signal trace, the distance between them and how long they run together, if they just cross at right angles, I wouldn't expect it to be an issue. My main aim would be to make sure the crystal traces are as short as possible.

I would not worry about the length or snaking of the trace. You are after signal integrity and low EMI, not to make it look nice. It is better to have a strange snaking trace on a PCB that works, than straight neat lines on a PCB that doesn't work, or doesn't work reliably.