[NiHaoMike]

Unless the compressor is labeled RoHS compliant (given it's a R410a compressor, it probably is), it probably does contain lead. Don't worry about it as it's nowhere as bad as the "environmentalists" say it is.

Put the service port in the liquid line. Depending on design, some can be quite restrictive and any restriction in the discharge line will degrade efficiency. (A restriction in the liquid line has much less effect.) Also, the heat of the discharge line can age the seals and cause leaks. The high pressure cutout can also be installed in the liquid line.

On a system of the size you're dealing with (physically, not tonnage), a shutoff valve in the liquid line won't be particularly useful.

A slight glass in the suction line might be useful for checking for slugging, but put it between the accumulator and SLHX. Two gauges are all you need, actually one (after the initial setup) since you can get a very accurate suction pressure reading with a thermal sensor attached to the outlet of the TXV.