Not sure if you are able to connect a sump for the RSM giving that it is suppose to be a plug and play.. you might need to drill holes
There are many different skimmers in the market to choose from.. A good indicator of equiptment is to see what are the skimmer experience hobbist normally use.. and there are different views about the situation you discribe (overskimming).. IMHO i think its better to "Overskim"
In Sump Chiller i think only have 2.. Iceprobe (not practical for your tank cos underpowered) and compressor (a titanium coil place in-sump)..
for the rest, yes, you would need a pump for the chiller..
Usually part of the sump design, likes of Filter socks, wool, and even the use of FR for PO4 remover.. you can also consider using biopellets..
HTH!