Text messages/website displayed on MAC
It sounds like you want to remotely prevent the Mac (which your wife has in her possession) from receiving additional data.

On your iPhone, go to Settings > Messages > Text Message Forwarding, and turn off forwarding for the Mac.
Source: http://www.macworld.com/article/2997176/software-web/how-to-remove-old-devices-from-text-forwarding-on-an-iphone.html

To stop browser history from syncing across devices, also sign the Mac out of your iCloud account. You can do this by signing into https://www.icloud.com/, visiting Settings, and removing the Mac from My Devices.

You may also want to change your iCloud account's password, which you can access via the iCloud account settings (Apple ID > Manage).