It states you MUST land, which means you can't by flying at the end of your movement. I believe this is to that you can't weasel and combine fly movements using jump jets. 30' is all you get (unless you have ways to increase this, such as Sky Jockey).
In no way does this say that landing ends your move action.
I've always interpreted it as you gain a fly speed with some additional limitations on height and landing. Otherwise you use the normal rules for flying.
It would probably help if you write that out with a little more detail. Something along the lines of how much you mean to run, out of how much movement speed, how much you're trying to fly, and how many actions you intend to use.
Trying to unpack this, a few things jump out at me. First, there is no specific "use a jetpack" action cost. A jetpack grants a flight speed, and normal flight rules are ised, depending on what you are trying to do in the air.
Second, with regard to using jump jets from a flying position, I can see 2 ways that that can be read. If you rule jump jets more flexibly, treating them as flight with limitations, as I prefer to do, because it allows people to use them without a lot of rules-lawyering, then you would not get any extra movement out of them that you didn't have with the jetpack.
If jump jets are read as requiring a special variant of your move action, as it seems your GM does, and some other people do, you would probably have bigger problems with stringing that all together.
Next up, jump jets don't ever jump 30 ft up, unless you take gravity out of the equation, though I'm not sure if that was a typo and should say 20 ft.
Either way, I don't see a reading that would allow you to go higher with a jump, a jetpack and jump jets than you could with just a jetpack and none of the argument.
Part of why I'm not sure of what you're asking, though, is that 8 don't know how many move actions you are describing. If this is supposed to be a single move action (and a reaction for descent thrusters), then it looks like you would be trying to use some of your run speed, and some flight, and the full movement speed of the jumpjets? If I am reading your intention correctly, that definitely can't be done as a single move action.
You should also know that there are two schools of thought about whether jump jets can legally be used with a trick attack, as they read "as part of a move action." Personally, I would allow them, but that is not universal.
https://paizo.com/threads/rzs2uljs?Trick-Attack-and-Jump-Jets
EDIT: If you have a jetpack and are confident in your acrobatics skill, you can probably save yourself an armor slit and not bother with descent thrusters. Anyone with a fly speed can attempt an acro check to negate fall damage, as a reaction.
What part of I am not adding extra distance to my move speed. I am doing all this in my allotted movement that I get so if I can move 60 feet as a movement I move 10 so I get up to speed for my jump. Then I fly 10-30 ft. Then with jet booster I either jump up 20 feet and 10 feet forward if I am trying to get onto something high or I jump upwards up 10 feet extra height and move farward 20ish feet while doing this I shut off my flight pack so I fall to the ground landing not breaking the rule for jump jets and not exceeding my movement.
The 60 foot movement speed is your ground movement speed. when you are moving in different modes, like flying, your limit is based off of that speed, not off of 60 feet.
So, with a move action, you can run 60 feet. With a move action and a jetpack, you can fly 60 feet. Running 10 feet, flying 30 feet and jumpjetting 20 feet is not something that you can do as a single move action. Because you would be flying 50 feet, and you don't have a fly speed that can handle that, even though you could run that distance along the ground.
Yeah, I don't think you can mix movement modes, even if you don't use up the full allotment of movement speed. One move action for land movement and another for flight, or vice versa.
For ease of play, I wouldn't bother with penalties while falling (especially if deliberate).
Installing multiple sets of jump jets would give you absolutely no ability that you don't have with a single set. The movement options they provide don't stack like that.
At lot of this falls under the questions I asked a few weeks back: Jump Jets Again. Still no answer or FAQ on exactly how the item works. Your interpretation falls under the third interpretation in my thread on it.
As of yet, everyone has an opinion and the FAQ is up in the air. The best we can do is make a judgement call as GMs and wait for clarification from Owen and staff at a later date. An FAQ update hopefully since it's been a year now with nothing new despite one new book release with another on the horizon.
There's three separate issues here and they might not have the same answer
1) can the jump jets extend your move, like if you move 25 feet with a 30 foot movement can you jump another 10 feet. (i would say definitely no)
2) Do jump jets end your movement? Like if you jump 10 feet up a cliff can you move 20 feet forward. This definitely should work. Its part of movement, not "instead of your normal movement"
3) Can you use jump jets to double jump? I think that should work. At the top if your jump you have the same momentum down (none) that you would standing. It also gives people incentive to combine the skill with tech rather than just saying meh tech is better i don't need skill.
I have a question regarding junpjets as well. They say that they can be activated as "part of a move action". A guarded step is a move action. Can jumpjets be used as part of a guarded step?
Definitely not. A 15 foot guarded step is WAY out of line for the power level of the boots.
The way I read it the limitations of jump jets is that when your turn is done and your finished moving you cannot still be in the air.
Not that jumping ends your movement but that when your finished, you cannot still be in the air because of a jump pack.
Or stated another way, you cannot use a jump pack in a way that you end up still in the air when all your movement is done.