Re: K5s What to do
 

This is a 100% standard steal attempt, and you flopped top pair. Folding is out of the question for now.

As I see it, there are three reasonable lines, assuming BB has folded and the pot is now heads-up:

1. Raise the flop, and bet a non-spade turn. This line has the advantage of getting in a raise against a very likely draw. It also might get paid off by something like middle pair that puts you on the flush draw. It has the disadvantage of immediately snapping of a bluff if villain is getting cute with the monotone board.

2. Call the flop and raise a non-spade turn. This line gets the absolute maximum from a flush draw. It might even fold out a small spade, which would be nice. The disadvantage is that villain might wuss out and not lead the turn.

3. Call the flop, call a non-spade turn. Passively calling down is sometimes the best line in HU pots. Monotone boards sometimes represent irresistable opportunities for villains to run three-barrel bluffs. It would be a shame to talk villain out of such a line. The obvious disadvantage is that calling down misses value from draws and weak pairs that would pay off a raise.

IMO, 2 > 3 > 1, but that's just me, and there's some merit in any of these approaches, and HU play allows you to mix up your postflop lines. The main thing is that you absolutely cannot fold this flop, and you should be tentatively planning on getting to showdown unless another spade hits or unless villain 3-bets you on the turn (if you go that route).

Re: K5s What to do
 

It all depends on what BB did. I'd call one bet, but not two.

Re: K5s What to do
 

I'm assuming BB folded, I would raise here. Generally I like to raise here with TP because villain will often think I'm raising here with a spade (which I sometimes am as well), & calling me down light. Lately I've found these sorts of donks generally to be a spade draw or MP/BP (sometimes a pp). Occasionally it will be TP with a weak kicker (hey look same as us!).

Although this is not exact evidence I tend to find the lower the limit the higher the chance the donk is a TP but this is completely speculative & not factual.