For 2.4km, keep running and try to time yourself if possible,
keeping in mind to beat your previous time (even 1 second is
good!). Personally I just longer distances and since I enjoy
running I do it frequently. Over time my 2.4km improved
massively.
On the other hand, there are those who advocate interval
training..apparently it helps a lot but I haven't tried it so I
won't know 
Pullups..practice also lah 
But
since you can do 4, I would say do multiple sets of 2, so do
2..rest..do 2 again..rest. Try not to cheat, i.e. not doing it from
a deadhang, kicking your way up, but I guess training frequency is
key here, so aim to do pullups every day.