I would get the cranking issue solved first. Modern computerized battery testers can only try to extrapolate how good the battery is. The only way to properly test a battery is to take a full load out of it. The proper procedure is posted on here many times so maybe try to have a look at that to. If the battery is good then check the connections and starter.

__________________
1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)