See the embedded pic for LDP location guidance.
In the 2004 TJ Service manual page, 25-14 PDF document page1684 the Leak Detection Pump is discussed in detail.
I hope this helps.
Im positive squeezing them will grab the relay pins, not sure how long they will last before they opens again thought. Slight squeeze in case they are very weak.
Correct, matching the length hole center to hole center. of course some small variation may comes in. I will suggest to replace one at a time so you can measure one against the other.