Drum Replacer , Snare hits louder at different times when using a static sample

Is it always the same hits that are louder? If so DR may just be mis-detecting the amplitude of the transient. You can check this by extracting the MIDI, and checking the note velocities. If that's it, and you really want all the hits to be the same amplitude, you can set the Dyn[amics] control to 100% to completely flatten the dynamic range or slightly lower if you just want to tame it. 
 
That said, I've sometimes seen the opposite problem that DR plays one or more hits exactly 6dB too low when restarting playback in the middle of a loop after pausing (i.e. stop without rewind). So there may some be some playback level issues even when transient amplitude is detected correctly.

Some velocity variation is to be expected unless your source track is from a synth playing the same sample at the same velocity for every hit with no other instruments sounding at the same time. If the extracted velocities need individual editing, you will need to take it out of DR and use the MIDI to drive with Battery as you described. DR does not currently allow manipulating individual velocities.
 
But, as I said, if you just want them all the same, setting Dyn control to 100% should take care of it.