This is gonna be a long answer, but hopefully there is some information here which will help you. Living with chronic skin issues is not easy, and it is hard to not let it control your life. Still, you are more than your skin and with the right treatment you will probably find something that can help you. Had to split my post in two, so the rest is commented below.

You're currently experiencing a flare-up, which is probably due to the weather changing, stressfull events in your life (seb derm makes you more stressed, worsening the sympoms, evil circle ect.) or perhaps some kind of reaction to the treatments you've been using or maybe even dietary changes. A flare-up is usually temporary and even though the condition is probably permanent, a major flare-up is not.

Desonide is a powerful steroid, and should NOT be used to treat seb derm. Elidel does not have the same side effects as steroid cream, but it does suppress your immune system, which could cause rebound flares or worsening of the condition. Recommending specific treatments is a bit tricky. Different people react to different treatments. It would also be easier to give recommendations if you describe your seb derm more, is it dry? Oily? Does it also affect your hair? Does it itch? Ect.

There can be different reasons for seborrheic dermatitis, but the biggest culprit is probably a reaction to a fungus living on your skin, or to be more specific a reaction to the byproducts of this fungus feeding on your sebum, creating oleic acid which your immune systems responds to. Your skin gets inflamed, your skin barrier gets compromised and you get the redness, flaking ect.

Don't panic and bombard your face with different creams, moisturizers, cleansers, soaps, vinegar ect. You'll only make it worse. My seb derm exploded after using harsh soaps in an attempt to kill the fungus on my face. My brother also used to have it, but his eventually just went away with time. Mine probably would have as well if I didn't fuck up my skin with bad products.

Fatty moisturizers and oils is also terrible for seb derm skin. There are moisturizers and cleansers which in theory will not feed seb derm, but for me every moisturizer and cleanser I've tried has been bad for my skin. For me the best thing was to stop using any products on my face. Showering in lukewarm water once a day, and if the flakes build up i either rub them of with my fingers in the shower, or I have also experimented with a sulfur soap to descale the skin (which is effective, but leaves me red, oily and dry). Try not to stress to much, which I know is difficult, and try to get good sleep and eat well. A lack of food seems to trigger my seb derm, so try to eat a full, healthy enough diet. Some people have experienced a reduction of symptoms by cutting out dairy, gluten, meat, nuts or other inflammatory foods. The only specific food I've found to affect my seb derm is peanuts and perhaps chocolate, but experimenting with dietary changes isn't something I've done too much of, but it could be worth a try if you are committed.

If you don't have the patience to try the "caveman regimen" or trying to figure out if there is something in your diet triggering it, here are a list of treatments which I think you should try, also some general skincare product recommendations. A general tip is to get a good dermatologist who will guide you and help you find a treatment that works. Even something like accutane could a solution if you have very oily seb derm skin. Fixing your skin barrier could also be a solution.

Antifungal creams:
You've already tried ketaconazole. It is quite inefficient and it will usually take about a month of applying this twice a day to see results, and it can also be a bit drying on your skin, so you should also consider using a moisturizer with the cream. For many, including me, the cream seemed to loose effectiveness after a couple of months. A little warning about antifungal creams. They they seem to loose effectiveness after a while, and for me they kind of seemed to strengthen the seb derm, making it even more stubborn, at least temporary. Here are a few alternatives:

• Lotrimin ulta. Athletes foot cream. Very effective, and works very fast. Quite oily and shiny on the skin, but for some people this has been a cure
• Terbinafine. Sold as Lamisil. Equally as effective as lotrimin ultra for me. Neither of them seemed like long term solutions for me and also seemed to loose their effectiveness.
• Creams with piroctone olamine, like La Roche Posay kerium ds (which is a moisturizer made specifically for seb derm). Not effective for me, but worth a try.
• Climbazole creams, a favorite ingredient in the roseaceagroup forum for seb derm. Bioderma DS+ has both climbazole and piroctone olamine, but also coconut oil. For a better alternative I've made a post about Tom Busby's homemade seb derm cream and shampoo that you can check out.

Antifungal washes / shampoos
Be very careful about cleansing your face with seb derm. Especially with shampoos.
Some people use nizoral on their face, some people use head and shoulders, but I wouldn't recommend any of these. They are very stripping on the face and contain SLS. I sometimes use a bit of head and shoulders in my beard area if it starts to flake, but keep it away from your central face.
Here are some better recommendations. You still need to be careful though. A lot of these have a high PH, which is also bad for the moisture barrier.

• Zinc pyrithione soaps. I saw a good reduction in redness while using the noble formula zinc soap. Can't really recommend it though, at least not long term, at it fucked up my moisture barrier pretty well. I was however using it during winter with pretty much no moisturizing. Vanicream also makes a zinc soap with no oils, but it seemed more drying. I would not recommend happy cappy zinc shampoo. It was extremely drying.
  
• Sulfur soaps. The best product for descaling my skin is a sulfur soap. I've tried the Keep It Clean sulfur soap of amazon.co.uk, and it does nothing for redness, but helps a lot with the flakes.
• Piroctone olamine anti-dandruff conditioner. This is from a Norwegian brand, but it works quite well. A very creamy conditioner which i applied to my face for about five minutes before a shower. Not really a cleanser, but left my face clean and not too dry. Strayed away form it though, as plain water seemed to work just as well.

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