Hi there and welcome to the forum
If the change in your circumstances is genuine, then creditors would be silly not to accept your revised offer - especially when they pushed you to accept far higher payments on the day of the creditors meeting.
If the revised offer is rejected, then bankruptcy is an option for you, but the decision as to whether you keep the car will rest with the finance company. Check the terms of the agreement to see if there are any bankruptcy termination clauses.
And there is nothing to stop you going bankrupt and your husband carrying on with his own IVA, although your Supervisor will need to separate the two estates.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
To have me propose an IVA for you, please visit:
http://www.melaniegiles.com/ivaEnquiry.asp
See customer feedback at:
http://www.iva.com/iva_companies/IVA_Advice_Bureau.asp