Welcome to the Pass forum, Liyla!
For me, your theory has some weak points, which you need to consider. I will mark just some of them, for now.
Even though he was the-last-minute-joiner in the group, there is no evidence of any kind, that he was into whatever spy relations. The most certain thing about him, is that he was a war veteran, who survived the Great Patriotic War (one of the not so many of his generation, being born in 1921), and that he was aiming for a higher degree in sports, which was the official reason he joined Dyatlov`s group. I have to admit, his past is somehow shady (which I personally relate to the conditions of the historical time period), but as well as his end of course. This is it. Totally no evidence, that he had any kind of relations with the US and the CIA. I am afraid, you are referring to one of the many myths with this one, because of the fact he wasn’t part of the official students group and he was older. This is well discussed in this forum. Too much of a speculation.
2. Murder at Kholat Syakhl.
Another popular version, which you read about already, since you are so sure about the murder. The injuries of the “ravine four” are far more serious compared to the other members of the group, that is a fact. But a human cause for them is hardly a fact. The whole environment there is quite hostile. Weather is unpredictable, and it is usually bad, with strong winds and bad visibility and low temperatures. Such injuries are likely to be the result of falling onto rocks, stumbling, wind, tree climbing and falling, snow walls falling (for the RAV4) and so on. Apart from this, there were no traces of other people around. Only footmarks of about 8-9 people. Adding to that, after they died, there are more natural reasons for the more speculative injuries (missing eyes, tongue) – natural decay and small predators, water, melting snow).
You say, that there were murderers – KGB or military, who tried to gas the group while they were finally resting inside the tent. Not to mention the tens of other ways to get rid of the hikers, your theory suggests, that the KGB/Military failed so bad, that they had to go back or wait, to finish the job. That is a rather HUGE underestimation of the abilities of both the KGB and the Army. If they wanted to get rid of one or more members of the group, they would have done it in a way, that puts no questions. The hikers might have disappeared without a trace, or drowned in the rivers, or who knows. But leaving nine (!) bodies, all of which were found, with various injuries, is a highly implausible scenario. Also, the murderers, would have to go through the same difficulties of terrain and weather, and what is more – they had to be aware of the groups route, which is quite hard to believe, or stalking them to the very end, in a highly remoted area, which is also hard to comprehend.
3. The tent
The condition of the tent, as it was found by the searching parties is a highly debatable thing. There is NO proof, that the tent was cut from the inside (a huge myth as well). The whole ordeal with the tent is related to a very bad handling by the searching members and the authorities later on. The “cut from the inside” is way more plausible to be the result of digging using shovels, done by the searching members, rather than the act of the Dyatlov`s group. The tent was literally dragged to the helicopters – therefore, all of the damage to the tent is questionable.
All my respect, but I think you need some more time researching here.