2500 does seem a lot. But it will barely reach the other side of the tank wehn all the rocks are. Guys who keep harder corals, anenomes and SPS corals sometimes have 50-60x in flow. So dont worry about adding another smaller pump. Doesnt have to be as big.
Skimmers...hmmm, basically
They bubble which forces dissolved organic compounds and proteins upwards which then collect in a cup which sits on top. Not 100% needed BUT i have ran my tank with and without and would never go back to not having one. The water looks a lot clearer, corals seem happier, The amount of gunk it chucks out is unreal and it can give you a bit of extra room for stocking too. For that tank you could look out for a 2nd hand deltec mce300 or a TMC V2 400, seen the later go for £30-£40 2nd hand. Its same skimmer as mine and i cant knock it. Paid £80 brand new for mine aswel