In answer to your questions:
1. I'm entirely sure what you mean, but if you're basically saying you wish to add other field to the job submission form, then yes this can be done with the use of the custom form functionality in JobRoller. There is no "response" section though, only an apply for job field which emails the employer/job lister, so additional customization may be required for your specific needs.
2. There are
other payment gateways available in the
AppThemes marketplace in the form of plugins, however none specifically for Ideal at this time. Outside of these, it would require customization on your part if you wished to use a different payment gateway.
3. Yes, you can disable the job seeker registration type, which in turn means that the resume section is not available at all. Thanks.