Yes, the theme is not encrypted and your purchased download will include all the theme files, so you are free to customize as you wish.
The 2 different registration types (employers and job seekers) is not available in the current version of JobRoller, however the next release v1.4 is imminent and will allow the two types. In terms of charging for listings, you can certainly choose to make listings free or not, but there is currently no function to charge for membership as such.
The search is based on the location entered during the job posting process. I tested this out for your country by typing in Tanzania, Kenya and used the "Find Address/Location" from the Google Maps field, and it returned "Tarime, Mara, Tanzania". Is this correct, or how you would expect to see it? Because this is how Google Maps has determined the location entered.
PayPal is currently the only payment option available in JobRoller, so it would require some customization on your part if you were to add other options at this time. In terms of manual payment you can of course set all ads to pending and add extra text to give payment instructions, but it means also a manual process on your part to collect funds and then approve the listings. There may be further payment gateways available in a future release, but these have not been confirmed as of now.