The short answer is: get a 12m kite.
The first step to extending your wind range is to get at least 2 kites, preferably 3.
Your biggest asset, by far, is your body weight, meaning that you should be comfortably powered on a normal size TT in 13-15 knots with a 12m kite, whereas 80 kg + guys would be underpowered on a TT. I was watching a friend of mine who is 50 kg Kite in 10 knots with a 12m kite and long lines on a 143cm TT, going upwind! The kite was barely staying up in the air... No chance I could pull that off with the same gear at my weight. However, I was well powered on the hydrofoil in the same wind.

It took me many years to understand that but below 15 knots, the type of board you use and your skill level are far more important than the size of the kite. Being around 85 kg myself, I used to swear that having a 17m kite was a must for enjoying light wind sessions, only to notice that below 15 knots it was really hard work and not much fun on a TT. My biggest kite is now a 12m and I no longer bother riding TT below 15 knots even if it's sometimes possible. Below 15 knots a light wind twin tip definitely helps, but you're really only going to mow the lawn anyhow.
Don't focus too much on which 12m kite to get, as long as it's powerful and has a very good low end, that's all you care about. Single strut kites are only an advantage when flown in marginal conditions i.e. 10 knots or less. In those winds, at your weight, you would need a very large twin tip to even think about going kiting with a 12m kite.
Just get a regular 12m and you'll be happy kiting in the 13-18 knots range with the same board you have. Below 13 knots, then I'd recommend you get into hydrofoiling! Believe it or not but I recently figured I only needed about 12 knots to get going on the foil board with a 5m Kite and long lines, where other guys next to me with kites as big as 18m are struggling on Twin tips...
Christian