Everything from your wall switches to your wires will cause you never ending problems.
Mechanical wall switches are still rated for DC. Houses USED to be wired for DC a lot. You only have to replace the stuff that was designed after AC was pervasive and wasn't engineered to handle DC.
(I forgot to mention that you'll also have to replace the light dimmers, too, along with most other electronic, rather than mechanical, switches. They usually use a current-zero-crossing turnoff device, and DC won't cross zero unless you force it to do so.)
Even if you replace your wall switches and outlets, your wires will degrade over time and develop holes and other blemishes that will cause a fire.
No they won't - unless they're wet (in which case you have bigger problems than galvanic corrosion). Electromigration at the current densities involved in house wiring is not an issue, nor is insulation breakdown. The wires and fittings will be just fine.