I wonder if you should switch to an automatic setting with the weight loss.
I have used CPAP for 25+ years as well. In my 30ies, I did lose weight and was able to come off of it for a period of time. I think it depends on the kind of Apnea you have. I know that many who lose significant weight can remedy their sleep apnea, particularly if it's obstructive apnea vs. central apnea.
I love the Dreamwear Nasal Pillow mask. I do find it sliding off some nights not as much since I switched to all automatic settings. I am a historical mouth breather and have worked hard to train myself to position my tongue resting in the top of my mouth which over time has made an amazing difference. I always struggled with a traditional chin strap. I have stumbled on something new that I think is going to work great. I just ordered a new strap for my Dreamwear Nasal Pillow mask. I curiously read some of the reviews. One person's review suggested that this mask should come from the manufacturer with two sets of straps. One that could be used as a chin strap as it keeps the mask from coming off throughout the night and is a a very comfortable chin strap. When my new strap arrived, I tried it with my old strap and it worked perfectly! What a concept!
No doubt CPAP Straps do take a toll on the hair and if too tight I can see it causing a permanent indentation. One of the things that has been helpful is to wrap a piece of silk fabric around the straps.
My preference is a nasal pillows mask but traditionally, I am a mouth breather. I have tried a chin strap and mouth taping. However, what has worked best for me is to consciously throughout the day to place my tongue in the roof of my mouth to create a habit of keeping my mouth closed. Over a short period of time creating that habit has helped me keep my mouth shut and ended the dry mouth most nights. I now find myself unconsciously and routinely resting my tongue day and night in the roof of my mouth. Just the awareness of realizing that when my tongue was at rest in the roof of my mouth, my mouth is automatically closed and I am breathing through my nose helped me begin creating that new habit.
I have a friend who had a reaction using a SoClean machine. It would be interesting to go back to your previous way of cleaning your machine and see if the issues you are having cease.
I use a 100% silk scarf to wrap around my strap to protect the friction on my hair. I notice when I don't do this that my hair shows my scalp where the strap has rubbed.
Do you know if you will be using a CPAP or an APAP? I was diagnosed decades ago and have struggled for years attempting to adhere to the PAP therapy. It was only recently since setting my machine on the automatic setting that I noticed a huge change. My scores before changing to the automatic setting were almost non-existent and now they range from 80-90 most nights. I do notice that the higher my nightly scores are the better I feel.
I think that many providers are not giving enough credit to machines that run on automatic. When I changed my CPAP settings to APAP, my life changed. I had good intentions every night going to sleep with my CPAP only to find it elsewhere in the AM. Since switching all the settings to Automatic, I actually wake with my mask still on most nights. My non-existent scores of the past because I didn't leave it on long enough to register now are ranging in the 80 to 90 range. A friend told me in some countries that APAP machines are actually sold at the local drug store as the settings will adjust to your needs.
I struggled for decades with various masks. I would begin the night with good intentions only to find my mask on the floor or elsewhere in the bed when I woke. My bed also looked like a warzone. My CPAP was on a pre-set setting. A friend told me to try setting the machine to automatic on all possible settings. This has changed my world. My sleep scores which really never existed before have just to great scores of 80-90 most nights. I think I was unconsciously doing exactly what you describe because of the set number. The automatic settings adjust to my needs throughout the night.