It's worth bearing in mind that you'll get very little skimate out of a brand new setup in the early days, so don't pull your hair out if you're not getting much performance out of your skimmer.
Make sure it's positioned correctly so that any bubbles produced are coming roughly half way up the collection cup neck.
See how you go in the short term, mid to long term you will probably want to replace the stock skimmer as to be honest it's quite poor.
I'd suggest buying a better water quality test kit, the 5 in 1 test strips are notoriously inaccurate and marine keeping is all about the detail. Salifert test kits for each individual compound are a good investment (start off with NH4, NO2, NO3, PO4, pH, further down the line you'll want to invest in some additional test kits which cover KH and Ca, Mg etc it you're thinking about keeping corals).
Not sure if anyone on here has latched on to this already but there is a strong petition circulating with the aim of reducing the phenominal levels of bycatch caught in seas across Europe every day.
In European waters over 1,000,000 fish are caught every day and thrown back in to the sea dead or dying, these fish are caught incidentally in the hunt for more valuable species such as Cod, Haddock and Plaice, fishermen are subject to strict landing quotas and often have no choice but to throw bycatch away to make ends meet.
The petition will go to the European Commision and requests a serious revision of the current quota systems, with revised quotas fish that were once popular could be back on our menus relieving immense pressure on stocks of our staple fish (Cod/Haddock etc).
Yeah, the plastic veneer/laminate on most chipboard stands will protect the chipboard from exposure to small amounts of water. But in time as the veneer peels or when the board becomes saturated the chipboard can start to deteriorate.
I have the same problem on one of the tank doors on my Juwel Trigon 190l, inevitably it will get splashed with water every week and the weeks and weeks of the same treatment have eventually started to penetrate through to the wood.
Not sure if you can proof MDF, I remember from Tech at school that it's not very good to paint, just sucks up whatever you put on it. That's about where my knowledge on the subject ends... lol
I'm no carpenter so I won't be able to offer much help with making a home built stand structurally capable of holding large volumes of water, but, I do think you will want to revise your choice of materials, MDF reacts badly to water.