I hate giving advice but........
FWIW, have a look at as many other job ads as you can find and try to benchmark your skills objectively, also speak to a few recruitment agents and ask them what they think your skills will attract but take their advice with a pinch of salt because they will tell you "oh I can find you a job for £xxxxxxK" to get you on the books but it will give you an indication of the marketability of your skills.
Remember that if they say "you would be considered for a car allowance" there is no commiment on their part to offer you one. Try to get in writing that you will get a review after 6 months and if you meet specific measureable criteria you will get the allowance, and this cant be something vague like "you meet expected performance" it needs to be black and white like "you sucessfully migrate our datacentre to virtual machines within 6 months" or "you deliver 8 customer SSL VPN's by Christmas" or whatever it is you do otherwise there is too much wiggle room.
I have to say I did it (changed industry and started at the bottom rung) I wouldnt do it now, just because I am older, but if I went back I would do the same thing again. If I were comfortable in my current role (as you sound like you are) I'd use the "slack" to train myself into skills in very high demand and then make the step and by that time the missus may have also found other work too.
To quote James Dyson, a mildly sucessful millionaire, "You can teach yourself anything in 6 months".