There’s good news and there’s bad news.
Good news is you can jump out of throws. You can also reversal them with a move that either has first-frame invulnerability or first-frame off-the-ground.
Plus, you can get used to pressing the throw command and also pressing it at the right time, in order to tech/throw option select. Practice just standing and throwing over and over from a distance in training mode untill you get 100% whiffed throws (no whiff anything else). Also try setting the dummy to throw a fireball, block, then throw when you come out of blockstun.
In the example of Ken jumping in with RH, you can hold up+back (or just up, if you have a good air game) to avoid getting thrown.
As for teching, often times you will fail at a tech because you didnt press the buttons at the same time (direction + 2k or 2p, actually – not 3p/k) or because you timed it wrong.
Playing as Ken against the CPU AI or another opponent and trying to be very aggressive with throws may help a lot with timing and spacing. EG. playing as Ken yourself and learning him well might improve how you react to him when you’re playing against him.
The very basic of throw theory is that throws counter blocking, since you can’t block throws. So in theory you would force them to block, or force them to assume they need to block, and then throw them while they are trying to block.
Bad news is throws are designed to be good. If your opponent is in an advantegous position for a throw in the first place, you’re already in a bad spot and will have to do some guessing.
Let’s take a look at some permutations after you block a j.RH:
They attack with a meaty punch
If you jump > you get hit
If you attack > you get hit
If you throw > you get hit
If you reveral > you beat their punch
If you jump > you get away
If you attack > you get thrown
If you throw > you get a tech (meaning damage and a reset position)
If you reversal > you beat their throw
They block/do nothing
If you jump > you’re in a vulnerable spot depending on direction and distance from corner
If you attack > they block
If you throw > could grab them, could whiff them, depends on distance
If you reversal > you are in a very vulnerable position for big punishment
Now, there’s also the odd variable of the opponent putting you in blockstun, then using a high priority/invulnerable move like a DP that will stuff any of your actions other than block. But therein lies the psychic DP and it’s very punishable if you do indeed block.
Meanwhile, it’s important to point out that in A3 there are two very important features to certain throws :
1 ) Some throws are “Slam” throws and will damage you a lot reguardless of weather you tech or not.
2 ) Against a lot of throws, teching will put you in a “reset” falling state where you fall on your feet – much like getting hit out of the air by a normal move. You can’t act but you’re invulnerable untill you hit the ground. The importance of this is that characters with very good mix-ups or rushdown/pressure games are going to see this as an opportunity/advantage.
Basically, while you’re landing from a tech they get the drop on you. But again this just applies to some throws, not all.
SO what’s the solution?
WELL, either don’t allow yourself to be trapped in those throw situations in the first place, or take a guess and hope you’re right.
In the example of Ken’s j.RH, your best option for avoiding a throw is to counter the j.RH – if you don’t, you’re going to have to guess what to do next.
 There’s some advanced stuff associated with this, involving option selects or vc activations, but ehhh… yeah…