Hi Richard and welcome to the forum.
There are many more qualified people who can help you but just to wish you luck with this process and sorry to hear about your circumstances. As you wife landed before the new rules hit this year you should be assessed under the old rules which will go someway to helping you.
Always use newest Set M form and they have a tendancy to change so keep an eye on them.
Need to book an appoinment at midnight as they are hard to come by and you can do this 28 days before the two years she entered up until expire of visa but it must be in this time scale. Appointments available are 42 days from today.
Read some threads here and hope it works out.