Maybe I'm not answering your questions specifically, but you're talking about a 635 kg MTOW aircraft... how much more do you realistically expect can be done? The R22 doesn't have the best safety record to begin with.
If you need more range/endurance, you won't ever get what you're wanting done in the until the pilots go on a diet or you pony up for the G2 (280 kg useful load) or the R44.