G'day Ian. I could be teaching you to suck eggs. Apologies if so, but it might be of interest to others.
It should straighten OK. Best not to attempt it cold though. The bend will have work hardened the aluminium to some extent, making it brittle. Bending it back while cold is a gamble. It's as likely to break off as it is to bend back. Even if you are successful at getting it back to the right shape, it's likely to be weakened and could snap off in use.
Aluminium is a little tricky because you can't use colour to tell how hot it is. Unlike steel that you can simply heat to red hot and then bash into whatever shape you want. Aluminium will melt well before it gets to any kind of colour temperature.
I've used the following method several times and it works very well.
Strip it down to the bare piece you want to straighten. That way you can put it in the vice and get a decent grip on the end with something like vice grips or an adjustable spanner. Once it's in the vice, put moderate pressure on the end with the vice grips as if to straighten it, but not enough to actually bend anything. Then play a butane torch around the area where the bend is (the bit you want to straighten). As it gets hot, you'll feel it soften and start to move. Hold a constant pressure on the lever and move the flame away and back again as required to maintain a workable softness in the metal until you've finished bending it to where you want it. It looks like it also has a twist in it, so you may need to move your vice grips to apply a bit of "un-twisting" torque.
The risk of overheating is not too great. You need about 350°C to get it soft enough to manipulate. It melts at around 600C, although it varies depending on the exact make-up of the alloy, so it's still a couple of hundred degrees away from melting. But if you get too enthusiastic with the torch, it can turn into a molten blob without any warning.
You can use an oxy-acetylene torch if that's all you have, but it's much more savage that a butane flame and can melt the aluminium in seconds. It's a bit like using a sledgehammer to drive in a tack. Use a small welding nozzle and keep the hot tip of the light blue centre flame well back from the metal. Only play it over the metal surface it in brief intervals of about one second at a time, or less once you feel it soften. I've done it with Oxy and it worked OK, but I was a little more apprehensive than with a butane torch.
If you've not tried the above method, give it a go. What have you got to lose? The lever is buggered anyway. Maybe practice on a bit of scrap aluminum bar to get the feel of it before doing it for real.
PS: You can use soap as a temperature indicator. Rub a bar of soap on it. When the soap turns brown it's at the right temperature for bending.
