It would seem that, in certain other situations, Changelings may have formed telepathic links with solids.
Apart from Odo's incident in "Things Past":
Evidence of Changelings Creating Telepathic Links with Solids
1. The Bashir Changeling
From StarDestroyer.net:
Founders can also mimic human beings to an unbelievable degree. The Founder that replaced Bashir for 4 episodes (from the change in uniform in "Rapture" to "By Inferno's Light") was completely undetected by changes in personality and even performed complicated brain surgery on Sisko that saved his life. Ron Moore confirmed that it was the Changeling impersonator that did this.
The implication here is that the Changeling who replaced Bashir likely had access to Bashir's mind, to an extent great enough to copy his personality, knowledge, and technical skills.
2. The Strategic "Simulation"
You say,
"An additional fact to consider is that we have no example of a changeling creating a link with a solid. There is no in-canon mechanism or example of this that I know of. If this ability existed then the dominion would have used this as a weapon or strategy over and over again during the Dominion wars."
Actually, there could be an in-canon example of a Changeling creating a link with solids, and in this case it would have been used strategically.
In "The Search (Part 2)""The Search (Part 2)", the Founders involve Sisko, Bashir, Dax, and O'Brien in a shared dream designed to extract strategic information about the Alpha Quadrant and to learn which kinds of concessions the Federation might make to ensure peace.
It's true that there is some technological intervention involved, but otherwise, the experience is identical in detail, depth, and realism to the link experienced by Odo, Sisko, Dax, and Garak in "Things Past".
The technology being used in "The Search" could be for recording the happenings in the shared experience and also for monitoring vitals and physical responses (especially to detect lying), rather than to create the experience itself. There is no evidence that the devices actually initiated the link between the Defiant crew members. It could be that a Founder initiated the link, and then the devices maintained the link while the Founder was away from the room, while also recording the link and monitoring vitals.
The Upshot
There is evidence in canon of other possible occurrences of telepathic links between Changelings and solids, and between solids and each other initiated by Changelings. Odo's creation of a link with solids in "Things Past" may not be so unprecedented.
