The Empire's actions make no sense

The Empire has this superweapon called 'Death Star', that can blow up a planet after just seconds of 'loading time'.

The Empire also knows the plans are probably on the planet Tatooine with the droids and all.

The Empire has NO qualms about murdering innocent people that have nothing to do with the rebellion.

The Empire has NO qualms about blowing up a planet FULL of such innocent people.

These are facts of this movie, and putting them all together, you have to wonder..

..WHY, oh, why didn't The Empire blow up Tatooine with the Death Star? That'd have destroyed the 'stolen data tapes / plans', and problem would've been solved. Reasons?

Also, why even kill Luke's foster parents, as if they had ANYTHING to do with anything, and why would Ben think The Empire would've killed Luke, too? I mean, Obi-Wan, IF ANYONE, should know that Darth Vader is Luke's father, and probably wouldn't instantly murder his only son, right?

Also also, why is Obi-Wan an important character? Was the rebels' plan to physically insert the 'data tapes' (still groaning over this one) into a droid, then send that droid to the planet where they - FOR REASONS - know that Obi-Wan lives, so this old recluse that hasn't been part of the rebellion for DECADES, can suddenly help them?

I mean, WHY would the rebels need Obi-Wan's help specifically? Wouldn't ANY old recluse be just as good? Why can't they go DIRECTLY to Alderaan? What really was the plan here?

Also also also, 'DATA tapes'. I will skip the ridiculousness of 'tapes' for now, but DATA?

If it's just DATA, why is Darth Vader so confident that they can get the plans back - he also seems to know where the plans are, so why not just go get them or blow up the planet, like I said?

I mean, DATA can be copied - how could it be otherwise? If you look at history of 'copying' on this planet, almost anything that can be made, has been copied in SOME way or another, it doesn't even have to be data per se, paintings, books, pictures, videos, etc. can be copied, Heck, holograms can probably be copied, too, in this movie's universe!

So why doesn't Darth take this possibility into account? Why CAN'T there be copies of that data all over the place, also transmitted to other ships and rebel bases and whatnot?

It's pretty bad writing to use DATA (tapes) as a macguffin for a story, when something less copiable (which is hard to come by, as I mentioned) would've been much better.

If the Empire doesn't realize that DATA can be transported in ships, pods, drones, etc. without life forms onboard (why wouldn't they?!), then wouldn't it have been a good plan to just copy the fjord out of those plans and just send zillions of copies all over the galaxy, by drones of some kind? (Which the rebels would most likely have in this kind of situation, or they're the dumbest rebels ever)

This plan is of course only in case rebels couldn't transmit DATA through space (which has been shown to be very possible in this universe), so there's really no excuse.

Logically, the Empire would not have killed Luke's foster parents, they would've just sent a CIA-like (I don't want to resort to the OTHER 'usual bad guys in movies' trope) group to the place, then wait there until Luke comes back. Surely they would've known Luke was away and should come back at some point. If they wanted to destroy the whole dwelling, why would they bother to play some weird game about 'scamming Luke to think it wasn't stormtroopers' that did it, but instead just orbital-bomb the place?

Why are they so adamant at doing all this ineffective crap and leave immediately after murdering those people, instead of just blasting the planet or at least its cities and such? I mean, does the Empire care more about the 'wretched scum' than the civilized people of Alderaan?

Just send the CIA-type group to Luke's home, then scout the planet for Luke and Obi-Wan, and then just do it in an 'official business' kind of way, as in confiscate the droids and anything that can contain data, etc.

But no, we will instead murder everyone, try to make Luke (that we know nothing about?) think that sandpeople blew up some trading establishment and LEAVE immediately.. WHAT?!

No matter how you think about all this, NONE of it makes any sense, unless Empire is absolutely not only idiotic, but probably schizophrenic, paranoid and completely insane when it comes to its actions and motivations.

I could wonder about the whole Obi-Wan trying to keep Luke's existence secret from the empire, then Leia (stupidly) bringing the Empire's attention to Obi-Wan, Luke and the planet, and why the rebels needed some old man as their errand boy, but I want to end this post before I am as old and frail as this errand boy the rebellion chose (for reasons?).