An APAP is affordable. I don't know why Sleeptech thinks there is a $2000 difference in price as the cost for an APAP is not that high. I recently bought online a brand new sealed in the box Phillips Respironics Dreamstation Auto Cpap with humidifier and heated hose for $400, paid for by myself, not with insurance. It works great, and was really easy and comfortable to use.
I also had nose/sinus pain after using a nasal pillow mask so I switched to the Wisp Nasal mask and the nose/sinus pain went away. I did not like have air blowing directly up my nostrils, it felt much more comfortable to have the air blowing in front of my nose instead. I haven't tried a full face mask yet. I had no leaks and low event numbers with both the pillow mask and the nasal mask.
Feeling stuffed up might improve as you continue using the cpap, but if you have a real cold, you might need a full face mask during times of serious congestion. I had some congestion when I first started using the cpap but that seemed to improve as I continued using the cpap. I started with a nasal pillow mask but it made my nose sore too, so after a week I switched to a nasal mask. After a few days of the nasal mask my nose and sinuses no longer felt sore. Many people like the nasal pillow masks, but I ended up liking the nasal mask better because I preferred breathing air that was blowing into a space just outside of my nose instead of having that air blown directly up my nostrils. I got a 'FitPack' that had 3 sizes of nasal mask cushions and chose a size larger than I needed because I wanted to have a good amount of airspace around my nose, and even though it was a bit bigger it still fit well with no air leaks. Regarding your settings: you'd have to talk to your sleep doctor about the settings on your type of cpap but I am using an Dreamstation auto cpap and I found it harder to breathe at the lower setting and breathing was actually easier for me when my setting was adjusted up. My auto cpap also has a Flex setting which helps make it easier to exhale so that likely helps as well. Stick with it and it will get more comfortable at some point.
I too had edema after my first week of CPAP use. Before CPAP I was getting up 3 or more times a night to use the bathroom (more than once is called 'nocturia'). I did research and found that sleep apnea is a common cause for nocturia as poor sleep changes the release of an antidiuretic hormone in the body. Once I eliminated the sleep apnea with the CPAP the nocturia went away, which is a good thing because its not good for the kidneys to be working overtime at night when they need to rest. You'd think more doctors would know how CPAP use affects the kidneys, but maybe not. I was very happy the nocturia was gone and I was determined to continue using my CPAP, so I had to find other ways to eliminate the new edema problem such as reducing my salt intake and elevating my legs more often. The edema has improved and I expect it will get better as my body adjusts to using the CPAP. One night recently I wasn't able to use my CPAP and I had to get up 4 times to use the bathroom, and the very next night when I was back on the CPAP again I didn't have to get up once. So there seems to be an immediate negative affect on my kidneys when I don't use the CPAP which helped motivate me to continue being diligent in using the CPAP. By the way, I also used a humidifier and using it or not didn't seem to have any affect on my edema so I have continued to use it as needed for nasal comfort. I hope this helps.