RE: what cardio can i do
The bleep test is, I presume, run between two points gradually having to speed up to make the cut.
If so then you are being forced to work against an increasing oxygen debt.
In this case then interval training (sprints) where you have a relatively short recovery period between each sprint is your thing. You repeat these to exhaustion. Hopefuly, after a wee while, you can go for longer before exhaustion.
Also some flexibility work so that you can touch and turn after each sprint. This should stop you falling on your arse or turning your ankle which becomes very easy once you start to get knackered.