1) West Slavic operated metathesis without lengthenment: CoRC> CRoC, CeRC>CReC

That's not entirely true. See Czech kráva, Slovak krava and Kashubian karwa. Or Czech mléko, Slovak mlieko and Kashubian mlékò.

All these words show signs of lengthening (and yes, Kashubian, even if it appears to have no long consonants does have long consonants).