Low Low Low cost liquid thrust chambers...

The very premise of what I’m trying to do is low cost as a primary design goal.
One has to question ALL of ones assumptions…
I personally fired the first ever 3D printed Regenerativly cooled liquid rocket engine.
ever fired in the world (2009)
I’ve done a lot of work in that space. The 3D aluminum costs are coming down….
Its cool high tech and in many ways awesome. Its also the single most expensive hardware component on my rocket by a factor of 3. For the long term business case to work I need to get the single 6” 24 foot tube cost ready to fly under $2K.  A die cast aluminum inner with a saddle jacket outer made from injection molded saddle and thin wall extruded aluminum outer is a rocket motor with a cost of under $200.00   So for the next generation of motors I’m going to abandon the 3D printed motors…
The first rocket motor I designed my self, and the 2nd liquid rocket motor I ever fired was saddle jacket, and  this generation will be as well. (113 Sec Fireing) 

 I’ll use machined aluminum done on my CNC lathe /mill as a stand in for di-cast aluminum. And the Saddle will either be machined aluminum or possibly machined polyethylene as a stand in for injection molded. 

Fusion360 cad beg...

I'm tryingto convert from Rhino to fusion 360.

The following was done in rhino, I'm trying to learn how to do the same in fusion...

I can easily draw this in fusion a Extruded cylinder with a hole in it.

I Can also draw my o-ring groove in fusion....

In Rhino I next draw two spheres.....(Blue and green)

Then I generate the line where the spheres intersect the cylinder.
(Inner intersection lines have been removed for clarity)
(I did this twice and the blue/green colors swapped  sorry for the confusion)

I then use the sweep2 command in Rhino to make a solid from o-ring profile and the two "Rails"
This is correctly tangent to the cylinder surface and has the correct o-ring breaks, radis etc...

Then subtract the solid and I have my o-ring grove.

So my fundamental fusion 360 issues....
I can't draw the spheres based on points, only dimensions. The lower dimension is easy to derive its the hole radius +the oring offset. The outer sphere is a lot harder as the oring groove sides are not straight and while I can place a point in the appropriate place fusion won't let me draw a sphere to the point. That problem I could work around with some triganometry, but the 2nd problem I can't seem to solve. I need to create a pair of lines to sweep the pattern, these lines need to be the intersection of a sphere and the cylinder. I can't seem to create this geometry no matter how I try.

Advice welcome.