You always use the same thread in the bobbin that you use as top thread. The biggest thread you can comfortably use in your machine is 138. I have sewed with 207, but you have to go very slow, and be prepared for failure, it was not easy to do.
You can start the machine at any height, but you either need to hold on to bobbin thread and top thread at the same time, or drive the needle through the work by rotating the wheel by hand first and then start sewing.
135 x 17 is a needle system, not a size. Needle system for all Singer 211U other than the 211U157A and 211UTT is 135X17. There is no such needle system as 136 X 16 that I know of.
The size needle you can use can be anywhere from a 16 to a 24. If you want to sew with 207 thread, use size 24 needles. Size 22 is fine with 138 thread.
No one lives forever, the trick is creating something that will.