HU versus FR questions, and advice would be great

I play $50 NL on PokerStars full ring and i haven't logged enough hands at that level to know if i am a winning player or not, but i am in profit from that level and i think i can play it relatively well.

Anyway, today i got curious and wandered onto this section of the site and started playing some heads-up. Needless to say i plunged into the deep end and lost $100 at the $50 heads-up table fairly quickly.

My main problem was calling with marginal holdings i think. The 2 different players i played against were extremely aggressive and bet near pot every street seemingly whenever they had raised pre-flop.

Now this is where my concern lies, because there are only 2 of you, the cards you play are expected to be weaker everytime you are in a pot, because if you had 20% vpip at heads up, i'm pretty sure they'd suss you out quickly and blind you down...

So i have a few queries:

Against unknown villain at a headsup table of $50 nl (which seems to be the lowest at stars bar the SnGs (more on that later)), what are your ranges of hands to open on the button? When limped to what hands will you raise with?

How do you judge strength of your hand vs villain on flop? Is there a lot of bluffing going on or should i normally respect raises as top pair for example. I ask this mainly because in order to buy the information you'd have to spend half a buy in just to get through the river.

Most importantly i think: What is the minimum hand you would a) push all in, and b) call all-in? Is TPTK in heads up usually a favourite against heavy aggression or is it still a set/straight/2pair+?

I ask these questions of you heads up gurus to guide me :P For you see i raised with any A/K, Qxs, PP and every now and then with suited connectors.

I found that when i moved to the SnGs even at the $30 buy-in level i was able to beat my opponents and with 0 suckouts (on my side). This might be because of the tourname structure of it rather than cash i do not know.
I read on another site that SnGs are better because of the rake in HU is appauling, is this true?
Do you prefer cash or SnGs?

Oh and i assume the $/hour of a heads up player at $50NL is a lot more than that of a full ring player playing $50NL FR? Are HU SnGs, or even HU in general harder to improve at past these levels?

One more huge thing i noticed was that once a player is in the pot sometimes it's hard to get them out! Like raising with draws never seems to get rid of them. Since they are only draws and normally we are not likely to improve, is it best to raise them or just check/call until we hit?

I know i asked a lot of questions, hopefully some of you can answer some of them :)
Any and all help would be great :)

Clar

Read my ISF's HU thoughts a bit down the page, should give you some answers you are looking for.

If you're simply interested in winrate you'd be surprised about how tight you can play and win a lot of money.

I had a read and it was very helpful thanks, just all the things mentioned are very general and i was wondering about a few other things like 3-betting and betting with a-high etc.

When you say you can win by playing tight, do you mean like only raise with A10+, Axs and PPs for example?
Does this work when playing the SnGs? Or is it just a cash game one?

Thanks,
Clar

HU is almost all about reads. I tend to play relatively passively at the start until I get a feel for Opp. Once you feel you have some ability to read them, its all about ranges and possibilities. You ask yourself 'how likely is he to have what he's telling me he has?'.

So its very situation dependant. I might be happy to go AI with TP decent kicker v's one opp, but require a set or better v's another. Heck I've called AI with middle and possibly bottom pair before because my reads are that opp is semi-bluffing a draw and won tournies.

Basically, you can value bet a lot more in HU than in FR games. I had problems today playing full ring because after playing one week only HU I was putting too much value in my TPWK and stuff like that. In HU, you can often three barell for value hands like TPWK, especially with aggressive image, while in full ring you need to control the pot and you are better off checking one street, only double barrell. Also, middle pair can often be bet for value on the river in HU. Not always. You have to get feel for these situations.

Just some advice. It costed me some money today.