I can't take this anymore. You are underexposing badly. In digital photography, if you underexpose, you can't really fix it without adding noise. You can't just add light with LR retroactively; if you didn't collect it, it's not there. Now let me help you out. I'd like you to see some success. You want to slightly overexpose in digital if you are going to be off in your metering. +1/3 is best, but +2/3 and +1 are salvageable, as long as you don't have blown highlights. For instance, in landscape photography I meter off the sky, set the shutter speed accordingly, then expose +2/3 typically. If I overexpose slightly, that's not a problem in LR, underexposing is.
Your porch photo is difficult because it's a high contrast situation, much like shooting in the woods on a hot sunny day. In that case, meter off the brightest face, then exposure bracket, 5D Mark III will do a bunch of bracketing, I'd do -1/3, 0, +1/3, +2/3, +1. Pick the best photo. When you get better than shoot only on shot with no bracketing.