Hi Lex, I'll try be constructive. I think the concern here is that the safety system on your 03 compared to an 07 would be considerably different. A bow has been suggested as some say they are easier to learn on.
At 78kgs I would think you could hold down a 14m in 10-18 knots as said. A newer kite for example would increase your wind range due to improved depower in kites.
I asked all the same questions not so long ago. With pumping the leading edge, you don't want to go rock hard as you may be crashing the kite hard for a few weeks yet. Still pump it firm 5-6 Psi so it keeps a good shape, you don't want it buckling. Don't bother with the knots on the pigtails just put them all on the same knot until you have a better idea. Always check your lines twice, middle front line to LE outer/steering/back lines to TE
My suggestion would be, if getting a new kite's out the question then ask a friendly experienced local to have a look at the safety system. Then reherse using it several times on the beach with someone applying tension to the line until your sure you can activate it in a hurry adequately. remembering when things go wrong it happens fast. Every millisecond counts when your hearding towards carpark/rocks etc.
Once you feel confident about yours and the publics safety go and do some more body dragging(in water). Try and get use to the pull of the kite going through the wind window. Once you've done that for a few sessions grab the board, you'll be up in no time with some persistance. Before you know it you will be looking for new gear, checking trees trying to guess the wind strength, thinking up lies to get out of commitments you already had before you knew it was going to windy. The list goes on
Hope some of that helps GL

Forgot to mention a refresher lesson would always be worth while. Can forget alot in 6 months...