Dynamic RLS not working in Datamarts as well as not being able to SUM decimal values

Hi,

I'm using PPU. I've setup a Datamart which feeds off of a Premium Dataflow in the same Workspace and have found the following issues:

You're unable to setup Dynamic RLS, Currently we use the following DAX to apply our RLS (Users joins to RLS one to Many and Locations joins to RLS one to Many): 
[Location Key] =
LOOKUPVALUE(
'RLS'[Location Key],
'Users'[UPN], USERPRINCIPALNAME(),
'RLS'[Location Key],
'Locations'[Location Key]
)

I'm unable to see how I'd recreate this using Datamarts.

Finally, I've got an issue whereby all the Fields I pull in from Dataflows which are Decimal Numbers are unable to be summed at Measure level or even just by settings the Fields default to SUM. I receive the following error message: 
Error converting data type nvarchar to bigint.. The exception was raised by the IDataReader interface. Please review the error message and provider documentation for further information and corrective action.

Any help would be great.

Thanks

Jack