Updating this as I find additional information.
As to your first question, who owns the Dragonlance intellectual property, that appears to have always been Wizards of the Coast. According to Tracy Hickman, the co-author of the core trilogy:
We were not unique in this: everyone working at the company at the
time was under similar constrictions. We were being paid to create and
play games and it was a condition of that employment that we hand over
our rights to our creations. Those rights were sold as part of the
purchase of TSR, Inc. by Wizards of the Coast and then subsequently
owned by Hasbro when they acquired the company as a subsidiary.
As to your second question, regarding a court battle between Weis and WotC, I was unable to find any mention of such a case. The closest I found was this:
Wizards continued to publish Dragonlance novels throughout the ‘00s, but they opted not to release additional gaming books. Instead, they licensed those rights out to Weis’s own company, Margaret Weis Productions (originally: Sovereign Press). The result was the most prolific period of Dragonlance publication since the early ‘90s.
According to Wikipedia, those licensing rights reverted to Wizards of the Coast in 2008.