Hmmmm....Well, you have at least doubled the weight of your vehicle and changed your position from relatively vertical to prone. So, that's pretty much what was to be expected!
The weight difference alone is the first issue.... No real solution to that, unless of course you can loose an equivalent weight off the engine!
As to the prone position, you are having to support the weight of your legs in that position - hopefully you are using clipless pedals and shoes, which helps but at least for a time you will have to adjust your thinking that no muscle power needs to be wasted purely to hold up your legs (seems obvious, but not necessarily so to your brain which has to make the spacial adjustment)
As to cadence, I find my cadence is always somewhat lower on my bents and even lower on my trike. This seems to be more of a problem for those of us who ride DF's as well to a great extent. If you ride the trike exclusively, it tends to come back up with experience and practice.
Speed......well, at least for a while I would try not to emphasize that....I doubt if it will ever be even close to what you had on your DF. Console yourself with the fact that in the right gear you can climb a wall and not fall over! Of course, where you are, it matters not.
My advice is forget the performance for a while and give yourself time to adjust and most importantly ENJOY THE RIDE!