As far as the panel goes, you're running her at 12v so your cable is rated for that. Unless the actual copper bit is the thickness of a hair then you should be fine provided your auto wire is rated at 6A as the max rating of the strip is around 72w per roll, so 72/12 (watts/volts) tells you that you're looking at 6A in total, 3A per output, on the DC side so you would be shocked at what is capable of handling the power. Easy way to check is fire it up and see if the cables get rather warm/hot. If they do, then upgrade your cables, otherwise leave them as they'll be fine.
Bending, I mentioned the top third of the stem for a reason. Even this ham-fisted idiot can feel where the stem is thick and hard and where it's "softer" so you get the "feel" for where it's safe to bend. I was scared of such things before, it's natural, and after snapping off a few bits found the "sweet zone" in regard to where to do it and how much pressure to apply. Let's face it, you don't make an omelette without breaking eggs, you never learn how to bend without breaking stems, the important thing is NOT making the same mistake twice and now I happily bend and and pinch stems without a care, even throwing S-bends in if I think things are too stretchy.
And to start another? A bit of mains cable, 0.75mm² is enough, think of an old cable to power a radio or such like with the socket chopped off and replaced with a lampholder, with a lampholder and a 14.5w or higher 6500K led replacement bulb which you have hanging around a foot above the new sprout. It'll take all that light and won't stretch to your grow light (which it will if my mental picture of your setup is right), and get it right and you can have a beast a foot wide in 2 weeks, but so squat you have no idea where to find the grow tip for topping and a stem that's so thick and solid you'll think there's viagra in the plant food.
Oh, just followed through the rest of the posts and see you took the plunge. I reckon it'll work fine, and now you can drop the light a bit, increase intensity and therefore growth, mainly because I had the vision of things being too far apart and a whole lotta stretching going on. Be aware more support MAY be needed as time goes on as she grows "top heavy".
But I reckon you'll do fine now, as new growth comes out the sides you might have to do some tucking and bending to keep everything at the same sort of level. Practice makes perfect, you WILL make mistakes so be prepared to and hopefully you won't lose as many plants as I have through sheer stupidity. And now the bug has bitten, all bets are off regarding arguments on spending money but remember you don't need to buy expensive branded stuff, as lemon juice is perfect to drop pH, additives for regular plants such as potassium are cheap as hell should you see a deficiency, epsom salts has been mentioned, bone meal is cheap as hell by the box for calcium, and when you buy the boxes of stuff from your garden/diy centre then the price you pay compared to some branded stuff "specifically designed for cannabis" drops considerably. Then you get her into the growing bug of tomatoes, etc, on the windowsill and suddenly these costs don't matter because she'll use the same stuff too (as I know to my cost).
