Santa Rosa sectional 10/3

I got owned on the following hand:

w/r I deal, I have QT9 xx KJxxxx Kx. I preempt an ugly 2D, and it goes

2D - x - p - 2H
p - 3H - p - 4H

I decide to lead the ST, we see

.........Kxx
.........AKJT
.........QT
.........Q987
QT9
xx
KJxxxx
Kx
.........A
.........Qxxxx
.........
.........

Declarer plays wins the SA, plays HA then a heart to the Q. Declarer now leads a diamond up.

I ducked, because partner is "marked" with the DA. If declarer had 5 trumps to the Q and two aces, surely she would have bid more than 2H right? I don't know what our 4 tricks are, they either have to be the minor suit aces and kings, or the DA and the CAKJ, or maybe even a slow spade instead of a third club. If I fly the K and declarer is 2542, oops.

Of course declarer has the DA and I just let her steal the diamond trick to make the contract.

I don't think I should ever get this one right. Thoughts?

There was a board where I freely bid a vully game and went down 3. That was sort of embarrassing.

Here's one board I think I should've gotten right. I have KQTx x x AQJxxxx. We reach 5C after I open 1C and lefty makes a takeout double.

The lead is a small heart, we get

Jxxx AJ9x Kxxx x
KQTx x x AQJTxxx

Unfortunately 4S is pretty good on a non diamond lead as long as spades are 3-2, but here we are in 5C.

I'm going to lose two aces, so I have to bring in trumps for no losers. I carelessly played a club to the Q, losing. I can only pick up Kx of clubs onside, but that requires the doubler to have doubled with three small clubs. Of course this is not impossible, but I don't think my LHO is capable of such a double, so I should've gone for the drop. It works on this hand.