Hi Mark,
In order to update the initial quota balances for go-live you can create 2 LSMWs to complete this task. The first LSMW would be to create the quota buckets in infotype 2006 and the second would load the entitlement amount to be added to those buckets using infotype 2013.
As far as loading "previous leaves" into the system. If you are specifically talking about loading absences prior to Feb, 2015 I would ask the question what is the purpose of having these records in the system?
Thanks,
Kory