Hi grm and welcome to the forum
With regard to the vehicle, I would sell it now as it is costing you money to keep. So long as you can demonstrate that all reasonable attempts have been made to effect the best price, then your IP will probably concur with this advice. If you have guaranteed a minimum dividend as part of the IVA deal, then you may need to pay over additonal contributions at the end of the arrangement to meet any shortfall.
If you take a job with a lower salary, then your payments will obviously have to reduce unless there are any corresponding cost reductions. IVA payments can only be lowered with the prior agreement of creditors - however some lenders are now stipulating at the original meeting stage that contributions can be lowered by up to 15% without recourse to a further creditors meeting - so you should check your own IVA proposals and Chairman's Report to see if you would fall into such category.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk