It is extremely unlikely that OpenWrt in a general sense is affecting your ability to connect to Disney+ and/or causing your wife's computer not to work properly. However, you haven't described what changes you made relative to the default configuration -- a misconfigured router could certainly account for these things.
When you changed your router, you may have gotten a new public IP from your ISP. Sometimes that can mess with the authentication for certain services, so you might try logging out of Disney+ and then logging back in again.
On your wife's computer, is it just IE that is having issues, or is it all internet connectivity?
The wifi on these devices is less than stellar in stability terms, I experienced disconnects and ARP or NDP failures for wifi devices frequently but this wouldn't be Disney+ specific it could be if certain devices like smart tvs have general connectivity issues though, esp IPv6 which relies on working multicast which seems to be less good on this device