Is it me or him ?

Hand 1: We cannot call a 3B with T8s. We can definitely not bet flop and not at all turn.
Hand 2: A8s can be 3bet if you know your opponent well. It wouldn't be a standard one preflop on BTN vs MP.
In both cases we have no FE (board hits villain's range) nor equity.

In any case, I think I see where is the flaw in your game. You try to bet for the wrong reasons. We only bet for value or as a bluff (sometimes we can adapt to capitalization of dead money, which in the end, still is a bluff). I think here on PokerStrategy there are some nice articles about betting but a very good book about this topic is from Andrew Seidman: Easy Game making sense of no limit hold'em.
Without math he explains right from the start why we are betting. I very much enjoyed this theoretical-driven part on this topic.

Hesticus

Thanks for advice, I will try to find that book. When it comes to Your answers :

1. T8s is my bottom yet standard defend on the BU vs resteal, I try to build my ranges to make sure my FoldTo3b stat won't go as high as 80% and higher thus I need some speculative hands here, and T8s imo seems decent as it has playability with flush draws and straight draws, has rather low RIO and isn't something that an average opponent here will expect on a regular basis thus higher IO when we hit well. When it comes to betting, I'm not saying I'm right, but from my experience on this position when people check on that flop after 3betting, it's mostly 2nd pair type of hand that they don't want to cbet on a dry flop with overcard and this is why i'm wondering if I should be more aggressive here to make that range to fold. Another part of range that checks here is either x/f , some AK x/c once and sometimes tricky made hand that sees more value by x/c. So by betting I'm aiming his second pair and A-high to fold but I'm wondering if by rather small sizing I don't encourage him to call.

2. Vs MP I 3bet most of suited Ax, has a blocker, it's suited and I don't call them. Maybe I could go rather for more SC but for now I 3bet mostly Axs and couple other hands.

You try to bet for the wrong reasons. We only bet for value or as a bluff (sometimes we can adapt to capitalization of dead money, which in the end, still is a bluff).

Well that's my question at some point, In similar spots, should I be more aggressive semi-bluffing - one - to make him fold weaker part of his range that beats me on the showdown but ( I guess ) should fold facing aggression - two - built up a pot in case I hit my draw. Because what I did for example in that hand with A8s, by checkbacking that turn pretty much I don't achieve anything - I never win on the showdown when I miss as I'm loosing with his 88,99,TT,JJ,AK and once I hit OTR, most likely that part of his range doesn't pay me off anyway but by being more aggressive I think I should make him fold that part of his range. Taking free card gives me nothing despite I will hit OTR quite often ... ?

H1 - You can defend but not vs everyone, imo. I prefer the passive line and do not like betting on flop or turn. You pour money in the pot and do not know how you can win it back.
H2 - It is ok as played.

I think that you should not try to make him fold anything with your hand. And it all depends on the board and type of villain.

I would approach these thoughts a bit more simple. We are playing micros and there is no need of going through great lengths of thinking in scenarios like this. We can almost play open cards at the micros. However, betting, checking and calling are extensively discussed in the book and would definitely recommend it

Semi bluffing: We do not semi-bluff unless we have 12+ outs or we have a huge amount of FE since this is far superior than your draw
folding vs aggression: We should fold vs aggression unless we draw to (basically) nuts. Keep an eye on this forum to see various situations in which we encourage to call or to fold vs aggression
Make villain folds weaker hands even though the hand is already weak: We should not be in this spot anyway. This means either you have called a too weak of a hand (OOP) or you don't know if you have FE from villain.
Pot inflation: We do not inflate pot without enough equity. That is, 12+ outs (if we shove we have around 45-48% equity instead of just a call, which is 24-25%) or we hit the board already.

1. Of course we can semi-bluff with less than 12 outs. With 12 outs on flop you can even go AI...
2. I do not agree that we should fold vs aggression all not nutted hands. Play according to odds is right.
3. Bluffing and trying to make him fold weaker hands is dull. The main reasons for us betting is to make weaker pay and to make stronger fold.
4. Keep the simple rule - bet with 50+% equity, xc with less acc to odds.