I would give Line6 a call or open a support ticket. If you have a full license and your computer is authorized you should not need to sign in every time.
ToneDirect is only for the Toneport / POD Studio interfaces in conjuction with the standalone PF software.
Currently the closest equivalent with the UX8 would be to monitor the Helix Native plug-in real time within your DAW or a standalone VST/AU host.
Download from where? Anybody can download tones from http://line6.com/customtone/browse/helix/
Do you have the trial version installed and running in your DAW?
Also, Helix Native has a bunch of factory presets. Click the Helix in the logo and restore factory setlists.
Still worth a search, there are many guides out there, for example Sweetwater has a fairly comprehensive one, maybe you'll find some new tips.
https://www.sweetwater.com/sweetcare/articles/pc-optimization-guide-for-windows-7/
To get started, create a power management profile for high performance. Also, if you purchased a mass produced PC form a store it's likely bloated and running unnecessary processes in the background (or processes that do not need to run until you need them). I would recommend doing some google searches specific to your OS.
Perhaps this is a temporary situation, if you have an strict requirement to not be connected to the internet, call Line6 or submit a ticket, otherwise I would give it another day.
Did you authorize the license? If you are still in the trial mode you need an internet connection. Line6 was having some authorization hiccups on their end
I doubt the interface is the bottleneck, I can monitor the plug-in in real time with no perceptible latency with a UX2 on a Win7 machine I built in 2010.
For tracking you could dial in a tone in PF and capture the dry and tweak the plug-in post processing.
You can play around with buffer sizes and also optimize your OS for audio production.