Sorry to hear Emmy, but sounds like you're approaching it with the right attitude, and you won't lose fitness between now and then.
There's still time for things to improve, and I'd say you don't really need to make a decision on what to do for ages yet (even as late as heading to the start line on the morning if needs be)
I'd say you're right to look at things in the long term. There's plenty of chances coming up to go sub 4.30, but if you go flat out this time and your injury's not up to it, you could do serious damage that takes months to get over. If you think about it, you've got the rest of your life to go sub 4.30.
Saying that, things could just suddenly click for you. They did for me. Two months ago I was wondering if I was going to even get to the start line, but things just started dropping into place, and now I'm aiming for a PB. It all happened really quickly. Problems became niggles, then the niggles cleared up. So quickly that I was gobsmacked at how it had turned around.