Toughness, elemental protection wand, and endurance, extended or empowered will give even a mage alot of staying power in a crunch situation.
Also use imp invis over stoneskin.The DR of stoneskin is seductive, but imp invis effectively gives 25%-50% more hp, makes your heals 25%-50% more effective, and increases the effective hp gained from endurance/toughness by 25%-50%. If you absolutely need stoneskin buy a 5-10 charge wand of it, and use it in an emergency. 250 gold per charge is cheaper then the cost to raise you at higher levels, and worth every gp if it keeps your blood pressure low from dying.
Sorcs really need to augment their spell selection with wands, and "cast from gp" what they cant cast from their blood given powers.
Also invest in tumble, something imp invis benefits as well, as it makes getting out of close combat even easier. Invest into a heal wand, and insta fire it, and move away if something even looks at you.
Feymancer also gets barkskin, so use that, and a shield/mage armor wand, and dex buff from Raznor to buff up your ac. Assuming 10 base dex, and min rolls from bulls, then with +1 ac from tumble, +1 ac from dodge ac/tumble boots and the above mentioned ac buffs you can hit 10 base + 1 min roll dex buff + 1 tumble +1 dodge ac +2 (1 dodge 1 armor) from mage armor, +1 ac dodge feat gloves, +4 from barkskin and +4 from shield. That gives you a total ac of 24. Not enough for first attack of most higher level creatures but offering solid protection from their second or third if you find yourself attacked. And if you have more then 10 ac at start, and roll higher from raznor buffs that gives you 2-4 more ac easily.
You should have a solid tumble score at 7-8 too. If you invest into it, its with the +4 tumble + 1 ac dodge boots 9+dex modifier which in your case is going to put you somewhere between 10-13 which is enough to avoid attack of opportunities alot of the time, especially with improved invisibility.
All this is not even taking into consideration the amazing tanking potential stag beetle form from polymorph offers with the ac and concealment buffs you have available.