A:AnswerThe max weight is on the mount box. Usually the mount weight capacity is far greater than the TV weight, because TV have become lighter over the years.
A:AnswerI do not believe that the vertical pieces are sold individually. You may be able to find them (if you are lucky) from a used seller, however I do not think that retail the pieces can be purchased individually. Contact the manufacturer for specific confirmation.
A:AnswerYes. Cable is easy to connect and too is USB. Both ports will only accept the the proper input cord, so no mix up. Just look at TV before they install and note where ports are. Or look at diagram in instruction manual
A:AnswerLook up the hardware spec for the size and thread bolts in the manual that came with your TV or the Rocketfish unit and buy them at Home Depot. Manuals should also be on line.
A:AnswerIf you have 41 inches of space above your fireplace you can figure you will need 6 to 8 inches of space below where your TV begins to allow space for a sound bar. Without a sound bar you can probably cut that down to about 4 or 5 inches. Make sure to measure the height of the TV you're getting to be sure it will fit in the remaining space.