Remo doesn't compose music. Whenever there has been shortcoming in the songs department, it has always been covered by the choreography as well as picturisation of the song. We have seen that happen in ABCD 1&2 as well as A Flying Jatt. Ofcourse he didn't have a challenge as far as dancers go in them.
Irrespective of whether Pritam composes music or not, Allah Duhai will feature in Race 3. How much Salman loves that song itself is enough to expect a reprised version.
Regarding cast, it's expected. You can't afford other stars when you've shelled out major budget on casting Salman Khan. Plust Salman if goes soft on his payroll then also he will be taking away chunk of Amazon prime as well as satellite rights price. Not to mention, couple of circuits distribution rights.