If you want easy mode, never leave sneak mode. EVER.
You can slam someone right in the spine with a warhammer, and they'll basically go "hmm, must have been the wind" as they collapse and you wail on them a few more times. You can execute enemies in several messy blows right in front of several bandits with crossbows, and they'll never figure out if you have legendary +5 sneak.
I recommend that you change the "confirm attack" button to "y" or something easy to hit instead of "Alt-y", though, since you have to press it a lot when killing unawares enemies.
As for shooting a crossbow a lot of times, remember macros. Drop all but ten bolts if you want to preserve your stacks, find a spot along a keep wall that has a ramp down just in front of a wall, record macro, fire ten bolts, collect your ten bolts, then step back where you started. Use Ctrl-U to set macro to repeat for 200-300 iterations based on character speed. Go watch TV or eat dinner or something. After that, it should be night time, so have your adventurer eat, drink, sleep, wake up, eat, drink, and do it again.
Around 1050 uses of a skill that gives 30 xp per use will give you legendary +5.
Also, animals seem to respawn, so if you find a place with a lot of large animals, keep coming back after a quick fast-travel. Sometimes, places like abandoned castles are great for finding large animals like camels or horses.