Personally, I prefer a trellis to be just about as tall as the vine is expected to grow. It depends on what you like... and what the vine is willing to do. I've seen lovely roses that were a couple stems for the bottom three feet, and then a mass of bloom upwards; and I've seen climbing roses clinging to the top of a fence for 10 or 15 feet. I have clematis that grows to 4 feet and other clematis vines that grow from 6' (in trellis) to 12' (those tall ones are happy covering an arbor). OTOH, ivy will often grow 20+ feet and requires pruning in an attempt to keep it within shorter bounds. Sketch your ideas out, and find out if there is something special your son would like to have. (Sorry, redwood trees don't grow well in Virginia, but a red wood playhouse might appeal.) If you can work something just for him into the plan as well as having him help plant and care for the new stuff, I suspect you both will enjoy the yard more.

How would you get a mattress up those stairs? A dresser? Spirals are great to access open lots above, but they totally suck to have for access to a 2nd floor. Your first fireplace pic is probably a electric one or a faux one. You cannot have wood that close to the firebox and it doesn't have a hearth. If the fireplace is as old as you say it is, then you need a chimney sweep out to inspect the flue. It may be damaged, but it is certain to be full of creosote. If the stone wall gets "hot" as you said, that's a BIG RED FLAG. It should only be warm to the touch. Your insurance company will want a report from a flue inspection before deciding if your home can be insured with that fireplace as active. My insurance company required that our fireplace either be redone or decommissioned. We chose to decommission and place candles in it. If you want to cosmetically redo the fireplace, you are looking at 3-5K. If the functionality is compromised and it needs to be rebuilt, then you are looking at another 3-15K, depending on what the damage is and which options you choose. Blocking off the flue and leaving it alone would cost you less than $500.

The items that you have in front of the electric meter make the area look more cluttered. ( add to the eyesore) You may be able to paint the larger electric box. - the same color as the house, so that it is not so obvious. Maybe find a nice large container and plant with taller plants. Be careful NOT to block the electric meter from view of meter reader.

show pictures of the overall space.