Where online can I find a completed CRM on PLT LFX?

Not only are you not the first LT to perform a Risk Assessment for a PLT LFX, you're not even the first LT in your company to do so.
While you can find plenty of completed DD Form 2977s for a PLT LFX, and there should be one or more somewhere in your company or BN on DTMS, they may serve as a decent point of reference, but nothing more. There are specific variables within your own company to consider, as well as guidance from the doctrine that tells us how to perform a PLT LFX and how to perform Composite Risk Management. There is also the actual training schedule that contains this PLT LFX on DTMS that will give you the tasks broken down in sequence of events and the names of NCOs that will be responsible for at least some of the control measures, and some specific installation requirements where this PLT LFX will take place, (they will have their own installation reg 350-1).
Long story short, doing this the right way will most definitely require accessing multiple .mil resources, to include .mil email to send to the BC for an O5 signature when complete.

"Prefer not to,log into anything .mil if possible." Good luck finding anything credible.

Google "how to conduct an Infantry live fire exercise" multiple hits to evaluate. There is an 8th Army resource not CAC protected.

https://www.amazon.com/Training-Circular-Infantry-Live-Fire-April/dp/ [login to see]

http://8tharmy.korea.army.mil/safety/Toolbox/Resources/Publications/tc7-9.pdf

Appendix A walks you through the CRM process.

Depending on which facility you are using, the range itself may have a CRM matrix for it just as it is built. Should be in the range SOP.

Search "Army CRM PLT LFX on Google. There 's lot of them posted
Here's another link:
http://www.benning.army.mil/armor/content/PDF/2017-2018%20Armor%20Training%20and%20Leader%20Development%20Strategy.pdf?29MAR2017