For the first, go into Journeymap options (J by default, then the button with a bunch of sliders) and there should be an option in there for death waypoints (the Waypoints dropdown, uncheck Create Deathpoints). If all you want to do is remove that particular beam, instead go into Waypoints instead (J -> the flag button) and click Remove beside the death waypoint.How do I turn of light beacon that appears after I die?
How do I turn off auto-sort in my inventory? It happens a lot, but I never notice what triggers it.
For the second, that's a keybind in Minecraft's Options -> Controls menu. (Inventory Tweaks heading, "Inventory Sorting")