Three questions to customizing `Ticks` in `Plot`, `LogPlot` and `LogLogPlot`

Question

When making a plot, sometimes I would like to alter the ticks and labeling of the ticks, in particular when doing a LogPlot or LogLogPlot.

Here an Example:

ticks = Automatic;

LogPlot[2/(3 Exp[3 x/2]), {x, 0, 40}, AxesOrigin -> {0, 1}, Ticks -> ticks]

There are a number of things I would like to change here.

(1) The x-Axis is now on top of the plot, so it would make more sense, and in many situation look better, to have the ticks below the axis, and the labeling {10,20,30,40} above. How can I do that?

(2) On the logarythmic y-Axis, I would like the main ticks to go in steps of 10^-3, rather than 10^-5. So from top to bottom I would like the labels to be {1,10^-3,10^-6,10^-9}, and between I would like to have small ticks without a label in steps of 10.

Now for two I actually know a way to do it, namely brute force specify the ticks manually like this:

ticks = {Automatic,
     {
      {10^-27, , {.008, 0}},
      {10^-26, , {.003, 0}}, {10^-25, , {.003, 0}},
      {10^-24, "10^-24", {.008, 0}},
      {10^-23, , {.003, 0}}, {10^-22, , {.003, 0}},
      {10^-21, , {.008, 0}},
      {10^-20, , {.003, 0}}, {10^-19, , {.003, 0}},
      {10^-18, "10^-18", {.008, 0}},
      {10^-17, , {.003, 0}}, {10^-16, , {.003, 0}},
      {10^-15, , {.008, 0}},
      {10^-14, , {.003, 0}}, {10^-13, , {.003, 0}},
      {10^-12, "10^-12", {.008, 0}},
      {10^-11, , {.003, 0}}, {10^-10, , {.003, 0}},
      {10^-9, , {.008, 0}},
      {10^-8, , {.003, 0}}, {10^-7, , {.003, 0}},
      {10^-6,"10^-6", {.008, 0}},
      {10^-5, , {.003, 0}}, {10^-4, , {.003, 0}},
      {10^-3, , {.008, 0}},
      {10^-2, , {.003, 0}}, {10^-1, , {.003, 0}},
      {1, 1, {.008, 0}
     }
    };

However this is extremely cumbersome, and I am wondering if there isn't an easier way to do it. Is there not a simple command that lets me specify the major ticks in steps of A, and the minor ticks in steps of B?

(3) Suppose I was satisfied with the default ticks that Mathematica makes for my plot. Then is there a way to manually add a tick and label at a special value, or I then have to manually specify all the ticks?

In the above example, for instance, could I add a single tick at x = 10.2, and specify a length of the tickmark, and position of its label? I know I could possibly do this by manually drawing a Graphics[Line[…]], however it would be a fiddling around to make it look good, adjusting the grayscale and thickness of the line. In the case of logarithmic plots, adjusting the position could also be cumbersome.

Answer 1

I will just answer the first question. You can use Frame/FrameTicks instead:

Show[
    LogPlot[
        2/(3 Exp[3 x/2]),
        {x,0,40},
        Frame->{{True,False},{False,True}}
    ],
    FrameTicks -> {{Charting`ScaledTicks["Log"], None}, {None, All}}
]

I used Show to add the actual ticks because handling of ticks inside of LogPlot seems to be suboptimal.