i have heard that kuomba is to beg ?? not to request ??
'omba' is more often used to mean 'request' or 'ask for'. It can still be used to mean 'beg' or 'beseech', but if you want to emphasize the begging aspect it's better to use 'sihi'
Would it be wrong to say "Unaomba kilo zaidi ya moja"? To me it makes sense because the "more than" goes with the "one", although I don't know if this is correct.