Your rainbow shark is a red tailed black shark. Not a rainbow shark, the red tail tends to be more aggressive. Though in a 250l tank should be fine.
5x Krib - What are the plans for these guys? You will find they breed like rabbits once the youngsters grow up.
1x Small Catfish - Really could do with gettin this ID'd, I think it my be in the Synodontis family...but other than that I'm not sure
1x Eel - From looking up the java loach, I really don't think that's what it is... maybe you could try to get it ID'd on here aswell?
8x Yellow Tipped Tetra - There's no such thing as a yellow tipped tetra...so I can't say if it's fine or not. Could you get a picture?
1 x Female fighter - What happened to her?
Have you already decided what pleco you want? There are loads to choose from, don't let impatiance lead you to getting one now...when you may well see a different one that you prefer more.
Eitherways, phone ahead to see if the plecs are instore. And if not, so long as they're common (which the ones I listed are), then they'll be able to order one or two in for you.
Please don't take this the wrong way by the way, but it seems like you're rushing...and not really researching before you buy...but more 'impulse' buying. There's no rush to restock...wouldn't you rather research everything first so you know you're getting exactly what you want? And not just what the shop has in at the time? Sorry if I'm wrong...but this seems to be what's coming accross.
Anyhoo, stocking wise (taking very rough guestimates as we don't know the exact ID's of each of the fish) I'd say you're about 90% stocked when you add a new plec. So have room for either another shoal OR the mollys/swordtails.
Then if you leave all of the new inhabitants to grow and mature over the next few months, see how things are going (check that your water stats are holding, ie. nitrates not climbing to high etc). If everything looks good (perhaps ask for assistance if you're not sure), get whichever group of fish you didn't get now. Ie. if you got more tetras, get the mollys/swordtails or vice versa.
Edit: Well there's some proof at least that the tank was overstocked, as the filter was clearly being overloaded. Now the plec imparticular is gone you should see both Nitrites and Ammonia return to 0. However if it were me I'd do a 50% water change now just to bring ammonia down to a safe level ASAP.
Also the nitrates aren't TOO high, but they're not great. You should be aiming for more like 20-30ppm normally (dependant on the reading out of your tap). I think you would find your nitrates would be much much higher if you filter was actually able to cope with all the waste though.
Edit 2: If those results were after a partial water change then this means they were even higher before!
A water change is never going to unsettle the bacteria enough to give bad readings... it's just physical proof the tank was overstocked.