Hi there and welcome to the forum
For every bad story you hear about an IVA, there are probably 100 other people who are quietly getting on with paying their payments with little fuss.
An IP cannot simply raise your payments without justification - so this could only happen if your circumstances improved sufficiently to mean that you could afford to pay more.
Your son is one of the most important things in your life, so of course it is important that you are left with sufficient petrol money to be able to visit him. A good IP will explain this to your creditors within the body of an IVA proposal.
You may be able to keep one specific source of credit to pay for your ongoing expenses (work related only) however this can only be done with the permission of your IP and the creditors generally - and importantly with that specific credit provider, and this would need to be cleared in full each month. I have occasionally done this quite successfully, so long as the justification is there.
You will need to address the equity in the property, and should take specific advice on this, as from what you have posted I cannot see any benefit in you continuing to pay your share of the mortgage. In the event that you were not to pay your contribution, this may spur your former partner into a quicker sale.
Do keep posting your queries and we will try to respond.
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