Vymystyc,
everything you're going through sounds familiar to me. I was devastated for the first week and could not believe it would ever get easier, but it did.
Take it nice and slow now. Your tongue is very confused to say the least about what's going on in your mouth right now but you will see how it will slowly adapt to your newly arranged interior decorations

Give it at least a week or two. I think for me it took longer, but on the other hand I've heard people get adjusted to their RPE sooner.
I was constantly worried about my speech and used to explain it to people all the time only to hear them say they did not notice anything strange about it. It sounds worse to you than others. And it will get better. Towards the end of my RPE era I didn't pay much attention to it's affect in my speech. All in all don't feel embarrassed about it. If it bothers you, tell people you have this thing going temporarily and get it off your chest. My experience is that people mostly felt for me and wanted to know if it was painful. End of conversation.
How is your tongue? Mine got very sore within the first 48 hours. So much so that eating banana was so painful it took me to tears. In time the tongue toughened up, but it looked funny through the whole RPE experience but once the appliance was out it got better very quickly. As your tongue hits the appliance every time you swallow it's bound to get irritated, but it won't be painful through the whole process.
Towards the end of wearing the RPE I practiclly ate anything, cut in small pieces. Things still got caught between the appliance and the roof of my mouth but it didn't feel so uncomfortable anymore. I learned how to use my back molars only to chew and how to work the food around the appliance. Your mouth can have unpredictable capabilities to learn new things!
For me the saliva issue persisted, and it still does to some extent, as I now have quite a massive appliance in too. For the first nights with the RPE in I slept with a towel on my pillow as swallowing was difficult because of the appliance in and because my tongue was so sore. After a week or so my mouth had learned to manouver with the excess saliva and could handle it.
Funny how the human mind works: I was so sure I would not handle the RPE and everything about it felt so intolerable in the beginning, but now I find that I have forgotten many details about how it was! I wrote down some of my RPE experiences in my braces journal "Joplin's impacted canines" on this board. If you wish you can check it out. You'll see how little I talk about the practical inconveniences as the story goes on. It tells me those worries really subsided little by little. My first days with the RPE are right in the beginning of the journal. I also kept a private, traditional diary at home. It helped me sort out all my feelings and keep track of the process while the RPE process was going on.
I'm very pleased with what the RRE did to my arch, so it was all worth it and it will be for you too, you'll see
I'm sorry this became such a long post. I'm just trying to say that although you may feel down and frustrated in the beginning, hang in there, it WILL get better!
I'll be gone for holidays for the next week, but keep talking on this board: there are many others here who have gone through the RPE experience. They helped me and they will help you
Good luck and congratulations on getting to the next level in your treatment!
Case: Impacted canines, crowding & crossbite.
Treatment: SARPE 2004/10/6, RPE 2004/9/28 - 2005/1/31, w-arch until 2005/11/22, impacted canines extracted 2005/5/18.
Braces on: top 2005/6/2, bottom 2005/8/30.
Braces off: 2008/6/9.
Retainers, phase one: expanding Hawley retainer 24/7, bonded retainers on top & bottom.
Retainers, phase two: Hawley on top, bonded both top & bottom, positioner for night time use.