Converting Intersection curves to normal curves

[Anonymous]

Doing my first model in Inventor I faced several problems.

First  of all, how to brake the link between 3d curve and original 2d orthogonal sketches? Or how to alter these curves without converting? 

I have a number of innacuracies, and this problem makes me use really weird mendings to connect the lines.

After, I tried to make a patches. Concidering Tutorial, there is three modes of using Patch, but I have no option, can use first one. What's more, some of chains of curves don't wanna be a patch with accurate nice edges, It's way more huge than I need instead. I checked, there seems no gaps in the chain.

And the last one that drives me crazy is thickness. Some surfaces can't be thicken, meanwhile the same symmetrical surfaces are thicken. Tried in both directions, with different thick. Inventor even displays a nice preview! But "peration didnt mergethe results of face-face intersection successfully" and "there's no meaningful result".

I would really appreciate your help, because I don't wanna be hopless designer of SAE bolids for my uni and struggle all their work 

[Anonymous]

the model:

[johnsonshiue]

Hi! To break link, simply edit the sketch of interest and go to browser -> right click on the reference curve like 3D Intersectionxx -> Break link. For Thicken/Offset, I would first create the surfaces and make sure they are smooth and intersections are reasonable. Use Zebra analysis to detect any unevenness. Then start thickening. I would not thicken on a per face or per surface basis, because you will end up with a lot of unwanted and unnecessarily complicated intersection edges. Does it makes sense?

Many thanks!