at levels 4, 8, 12, & 16, a character will receive both an ability score improvement and a feat of their choice.
characters can drink a potion as a bonus action. however, administering a potion to another creature is an action.
characters roll death saves in private, only they and the game master will know the result.
these options can be used once per turn, so no, they cannot be combined.
nudge fate. for 1pt of inspiration, you can tip the scales and add 1d4 to any attack roll, saving throw, or skill check. you can declare this after seeing the roll, but before you know the result.
accelerated recovery. for 1pt of inspiration, your wounds knit together much faster than most. during the short rest, you regain double the hit points of any hit dice spent.
spin the thread. for 2pts of inspiration, you can influence fate further and reroll any attack roll, saving throw, or skill check. you can declare this after seeing the roll, but before you know the result. you must use the new roll.
preternatural assurance. for 2pts of inspiration, you hope to predict the outcome of threats. roll the saving throw as normal, on a success, you take no damage. on a failure, you take full damage. you must declare this before you roll.
rider of the pale horse. for 3pts of inspiration, you can cheat death and auto-stabilize on all death saving throws. in the following round, you regain hit points equal to a roll of your hit dice + con mod.
shared avoidance. for a variable amount of inspiration, you are guaranteed an encounter-free night. the number of inspiration required is equal to the number of player characters resting.