Hi! Welcome, & good for you, giving your ds the best start!
I wish I could tell you more about how much and how fast you can pump & how a double electric compares with a single or hand. Unfortunately, it really depends on you & how your body responds to a pump. Some women get lots in just a few minutes, while others (even with a great supply) can hardly pump anything.
What I can tell you is my experience.
I've only used a medela pump in style advanced (double electric). It's taken me thru 2 boys, working all day. With ds1, I had to pump 3x/day (about 10, 1, & 4 if I remember correctly). With ds2, I was able to pump enough for his bottles by only pumping twice (maybe 10:30 & 2 or something like that). Even for me with different boys, my pumping was different. What really helped out both times was to institute a dream pump. Neither of mine ever really took to a dream feed, so I used that time to pump instead. It helped take the pressure off myself for trying to get enough only at work. So I really like your idea of pumping again at home. That really worked for me.
My PISAdvanced was pretty heavy, but I got the backpack version, so it wasn't really that much of an issue. It was kind of noisy, but at work, the whole hall didn't hear what was going on.
As for pumping on your days off... I didn't have to do that with ds2 (didn't have the days off with ds1). Some things that I've read on the boards though are... if you only single side feed, then pump the other side while/immediately after you bf. Or if you double (like me), then maybe wait an hour or so after a feed & then pump both sides. That should give you enough time to be prepared for the next feed, even on a 3 hr EASY. (BTW, several bf moms find that their lo's don't stretch to a 4 hour EASY as soon as Tracy suggested they might. Mine were still on 3-3.5 hr at 6 months or so. Not all do that, but I wanted you to be aware that it's not uncommon.
Oops. Just re-read that you do a df & pump for that. Not sure when you'd fit another pump at home in, but it would be good if you could get one.
Sorry it's late & my brain is kind of jumping around. You mentioned sending extra incase ds was really hungry. I did that the first few days, but once I figured out how much he was taking usually, I just sent that amount. AND I kept a bag of *frozen* milk at daycare in case of hunger, spillage, drop-in bag breaking, whatever. That way he had additional available, but I didn't have to send in a lot extra every day. Just a thought.
I know some have mixed ff & bf, but I don't have personal advice on that.
Don't worry about asking questions.
And try not to work yourself up. (Easier said than done, I know. I've been there.) But ds will pick up on it, & it doesn't help pumping output.
I hope something in that helped. Keep posting.