It would depend on your proposal and any modifications. However, a salary of £30k would net a shade under £1900 per month. If you received a bonus of £3000 in one month there would be tax and NI deductions of approx £1000. Your net would therefore be increased by about £2000 for that month.
Provided you are allowed to keep 10% of your earnings you would deduct £190 and divide the balance by 2 meaning you would pay in the region of £905 into your IVA.
Your own IP should be able to give exact figures and of course it depends on whether the bonus is paid all in one month or paid at various times over the year.
Yes but if the bonus is paid in one month it forms part of that month's income and is treated as such. You keep the first 10% of your increased income and divide the rest with your IVA.