Welcome!

The geometry on your Escape was designed for a rigid fork. A suspension fork is much taller, and will physically raise the front of your bike up by a few inches. It doesn't sound like much, but your head tube and seat tube angles will become much slacker (less vertical), and the bike may handle and ride pretty strange. I would not recommend swapping your fork for a suspension fork. If you want a suspension fork, then I would buy a bike with that from the factory, as the frame will be engineered with the proper geometry from the get-go. As an alternative, consider a carbon fiber fork.

Note that, depending on how you're buying them, you may need BOTH a hub assembly and a freehub. They're technically two different components, but a freehub is sometimes (often?) sold as part of the hub assembly itself. If that's what you're buying -- the entire hub and freehub together, then disregard this, but I would double-check that. In any event, you may find that replacing the rear wheel as an assembly will be less expensive than buying a hub because you'll have to presumably pay a shop to re-lace the new hub into your wheel. You'll likely also need new spokes, because the Deore hub will most likely have a different flange height than your stock Giant hub, requiring shorter spokes.

If you're a year-round commuter in Seattle, and ride wet roads often, I would seriously consider disc brakes. You won't be able to easily add them to your current bike, but they come stock on something like a Roam. You're planning to spend upwards of $450 equipping your current Escape, but you can out-and-out buy a new Roam 2 for $600. Surely, your local bike shop would offer $100-150 on your Escape 3 as a trade, making your financial outlay about the same (and then you get what you really want). You'll also have hydraulic disc brakes, which will be much nicer for wet weather commuting than rim brakes. I would be very surprised that you couldn't sell your Escape 3 for $150 on the local Craigslist. Around here, I think you'd sell that pretty quickly.