well, IMHO:
- drawing to a gutter is rarely a profitable so you should do it only when opted to check on BB, if you got those 4 straighty cards at least of an average strenght you can always hit a decent pair that will often beat your opponent's unimproved limped pair
- discarding 5 is something I almost never do (you usually have at least a TEN in your hand to keep)
- if he limp/reraise you need to consider if he can do it for bluff too
- also regs almost never limp in HU
- defending draws is IMHO never an optimal line
- pat bluffing: why not? as far as you make it in proper frequency
- 3x the BTN: the same as above, if you'll do that to often your opponent's gonna start responding with 3bets
- regs usually minraise in HU but because the are regs they will be adjusting their game to a specific opponent and a specific play
hope you like my answers