First and foremost is safety.................and it sounds like that Holly is way too close to the house. It is blocking the light that is needed to keep your house dry & properly ventilated...............not good for wood siding and it will create mold & green moss when the sunlight can't properly get thru. I would positively trim anything blocking the vision & light at the window. Any tree that close can damage the septic, cell pool, drain field, pipes in & out. I know they are beautiful, but maybe you could plant a new one 50 ft away and start timming that and eventually take it down. Those Holly leaves will cut you so be careful. I don't like trees to be higher than a roof..........think about a big wind with all those high branches. You mention haveing trouble getting to the back yard, these trees are overgrown and need to be super trimmed for safety & light.