Sorry for the delay in replying...
3) A #12AWG is adequate provided that the length of the cord is kept short. However, if the cord will be more than 5-6ft then you would be better served with a #10AWG cord and a 25-30A receptacle and circuit breaker. A short power cord (if plugged in) is covered by UL code and is more concerned with managing voltage drop than a hardwired Code circuit -- but if you are going to hardwire the compressor then go ahead and wire with #10AWG copper all the way. I haven't decided exactly where I will place the compressor in my shop yet...assuming I can get it running but for a 15amp motor, wouldn't #12 and a 20-amp receptacle (and breaker) be sufficient? I don't intend to wire a very long cord to the compressor. The main 200A panel (not a sub panel) for my house is in my shop so the maximum run from the panel to the receptacle would be no more than 20 feet.
#12AWG copper is fine if the cord is kept short in length (no more than say ~6 ft). If you need to run a longer distance then it would be best to upsize the cord by an additional gauge stepping to minimize the voltage drop (esp. on startup).
While the motor may only draw 12-15A when running, compressor motors are somewhat unique in that they have to start up and immediately begin working against a significant load (esp. when the tank is already pressurized). For example, my 3KW (~3.75HP) compressor motor draws about 15A when running, but for a second or two on startup it will draw a peak of 70-80A (the "
Full Locked Rotor" rating), which can cause quite a lot of voltage drop on a lighter wire gauge.
As for the circuit breaker sizing, if your current 20A breaker and receptacle/circuit and #12AWG wiring are sufficient to allow the motor to instantly start (with a pressurized tank) without struggling and you do not encounter issues with your breaker tripping on startup then all will be Ok as is and no need to change anything. However, if your motor struggles to start when the tank is pressurized or your breaker is tripping, then you will need to upsize all your wiring to #10AWG copper and a 25A or 30A circuit breaker to handle the startup loads without tripping. (Note: this would also entail the use of a 30A receptacle if this is a plug and receptacle circuit rather than hardwired.)
However, if you measured the actual running amperage of your motor (with a clamp-on ammeter), I suspect you will discover it is far less than the motor's plate suggests. My compressor has the same size (2.98KW) motor as yours and mine produces about 25-30% more SCFM than yours and can charge my 80gal tank to 150+PSI in about the same time as your 60gal tank reaches 115PSI. So your amp draws may be a good deal lower than the motor is rated for.
6) For the filter you can use an OEM replacement filter or you may find that your local automotive and/or lawnmower shop may have suitable replacements. Choose a filter with at least as much effective surface area as the OEM replacement, or even more if you wish, just don't opt for less. Just doing some poking around on Amazon, it looks like Solberg filters are decent quality? I guess I am supposed to consider the SCFM rating on the compressor to get the proper filter size? For this compressor it seems that the Solberg FS-10-050 would be appropriate.
The particulars of the filter aren't real critical so long as they do not add significant resistance at the intake (which can damage the reeds and result in burning more oil). The filter has two real purposes: 1) prevent large and/or sticky debris -- and especially damaging paint overspray -- from entering the intake and gumming up or damaging the reeds and 2) quieting the compressor noise, much of which escapes via the intake opening. Specs like "
1 micron" are of no consequence or concern with a filter like this as the filter's only purpose is to protect the reeds and quiet the compressor -- the compressor won't much care if some 0.001mm dust finds its way in as it will just pass through the system without consequence. So the most important parameter is adding as little intake resistance as possible (when in doubt, go a little oversized).
I recall you commenting that your current pressure switch cut-in and cut-off points are 90PSI and 115PSI.
I would change these to at least 100PSI and 125PSI if it were my compressor -- if not 115PSI and 135PSI (which is a really good compromise pressure range, IMHO). You really want your tank pressure to stay
higher than your inline (air) pressure regulator (by which I mean the
outlet regulator, NOT the pressure switch!) because there are additional pressure losses in your air pressure regulator, oil and water separator/filter and hoses. So if your nominal tool pressures are 90-100PSI (typical), you'll want
at least another 10PSI in the tank to ensure there are no significant fluctuations in the air pressure delivered to your tools during use, which will help to ensure consistent and repeatable performance (especially in nailers and paint sprayers where consistency really matters).
When installing the water/oil separator/filter and air pressure regulator, the water/oil separator should come before the pressure regulator so that its pressure losses do not affect your final air pressure. You can install these at the tank, but for best performance, and optimal water removal, you really want enough line (ideally metal line for heat dissipation) for the warm compressed air to cool so that moisture can condense out first since the water/oil separator can only separate liquid water (this matters most during paint spraying and extended air use, it matters relatively little when used with impulse tools like nailers).
I do share another member's concern that the large main pulley on the compressor does not appear to be shaped as a cooling fan (the pulley's supporting struts should be angled to act like narrow fan blades so that it blows air over the compressor head). If this is in fact the case with yours, then your compressor will run much hotter than it should since there will be no significant airflow over it. This added heat will also have the undesirable effect of increasing the amount of suspended moisture in your compressed air, which means more condensate will form in your hoses and tools. You may wish to look into replacing the pulley with a suitable compressor-type pulley. You could also opt to install a small electric fan situated such that it blows over the compressor when it is running, which would achieve the same effect.
I hope you are enjoying your new compressor!