Well As others have said, synthetics do not last anywhere near as long as down. Synthetics can be done badly or well done. Even the best of these only last about a year(15-30 nights) before they start degrading. I usually buy a 0F synthetic, not because it is warmer, but because it will last 10 years(360 nights) before it goes to 32F; average loss of warmth is about 3-4 degrees per year. Keep it CLEAN. Body oils, dust combine to form a low insulation value on synthetics and down. Some people sweat very little, some a lot. It depends on your metabolism. Down will typically last 20+ years assuming the same usage.
Synthetics only advantage over down is when wet or very damp. They are a bit stiffer than a natural down fiber. But, they will degrade quicker if you compress them. The harder, hollow fibers usually kink/compress together and do not have the resiliancy to bounce back. Down is mostly air and has some "stickiness" to it, so compressing it simply squeezes the air out; 30sec of shaking to overcome the "stickiness" will restore most of the loft and body heat will cause the fibers to return to their natural shape. Down will withstand higher heat (though not the shell/zipper.) Anything up to 200F(~95C) or so will not hurt it. It simply fluffs up more. This is from direct experience with flie tying. STEAM heat is OK to restore a matted fly be it a fluffy streamer or a dry. Every tight compression of a synthetic causes some loss of loft. You really shouldn't compress them a much less than 5:1. More is damaging to loft on synthetics. Typically 10:1 is OK with down.
The EN ratings all use some sort of covering over the manikin used as a heat source. We know that UL long johs are better than shorts. Mid weight are better than Lights. Heavy weights are better than Mid weights. Want to guess what is used during EN ratings? There is no weight spec. There are many out there that do not expect to need any coverings. It is all subjective anyway. Some people sleep cold and need a 10F bag for 32F. Some sleep warm, and need a 40F bag for 32F. It is very difficult to be accurate with temp ratings. US system differs. Even the loft (which is rated at EN800FP MAX, even Eider down) is different(US rating is 900FP.) The EN ratings are better, but still leave the manufacturors plenty of wiggle room.
Anyway, this is your subjective experience. All I can do is recommend some methodes to keep you warmer.
1) Wear Long Johns to bed. These will add minimal bulk and weight and give you the extra warmth you are looking for. Long, sleeping socks, too.
2) Drink a cup of hot cocoa before bed. Use the bathroom, then turn in. This will add "some" warmth without too much liquid forcing you to make midnight runs.
3) Eat a candy bar. Chocolate is prefered because it has fats & oils (lipids) for long term fuel and slower digestion...and sugar to help you get warm.
4) If you get cold, do some sit-ups. Waking metabolism is faster than sleeping metabolism...energy burned exercising will warm your whole body eventually.
5) Heat a bottle of water and put it into the bag.
6) Put any extra cloths (damp cloths are OK) in your bag. Though this may cause loss of loft with down, it will act as extra insulation and reduce air pockets making your bag easier to warm up.
7) Insure you have good ground padding. I assume you do. But, 1/4 of CCF pad is no where near as warm as a 3/4" NightLite. NeoAir's are not as warm as Exped Down Mats or Stephenson's DAMS. You should use the correct one for what you expect and how you sleep.
8) Sleep under a lower tarp or tent. IR acounts for about 10 Watts of heat. This can be held with a roof, but it needs to be fairly close to you. No more than a foot away or it starts loosing effectiveness. Closer and you have a lot of condensation. This depends on your conditions, of course.
9) Not recommended for long term, but for a night or two you can cover your head under your bag. Down will degrade with condensation, but it will warm you for several hours(3-6.) Synthetics get wet but perform similarly. Make sure you can dry your bag in the morning, though.
10) Light a candle. The psychological effect is worth it in a tent or under a tarp. Be carefull. It might add another degree of warmth in a small tent.
11) Choosing ground by avoiding ridges, mountain tops and fields. A pine tree often makes a good shelter, blocking winds and draughts. Pile forest duff under, around your bag. It will add some warmth. Avoid shore lines near lakes and rivers. Aviod valley floors.
12) If a fire is an option, build one. You may need to stoke it several times over the night, though. Waking metabolism is faster than sleeping metabolism, so, it may be uncomfortable with waking every couple hours, but I know it helps.
13) ANY dry clothing you have, put it on.
14) Put your pad inside your sleeping bag, if you use an inflatable. It will benefit from edge losses and be warmer to sleep on. It also reduces the volume inside a bit. Be carefull NOT to compress your bag, though.
There are probably some others that I forgot. I typically head into the ADK's in spring and fall with a too-light bag. These "tricks" work.