A friend wrote me: 余計 ありがと、 きにするようにして I know first part is "Thank you so so much" second part I understand the parts, but I can't put it together into a decent meaning. きにする is to worry or care about something. ようにする is to try to do something. I guess して is here not meant as an imperative, but because this part should be before the "Thank you" part (sentence order is wrong, due to last part being added), but even then can't really figure it out. Something like "Thank you, that you try to care for me"?
~して can be used as the connective form of a verb in addition to being an imperative, so you're correct about it coming before the "Thank you" part.
However, ~ようにする can also mean "making it a point to do~".
To put it all together, I would translate 余計 ありがと、 きにするようにして as "Thank you so much for taking the time to care about me."