Macro for calculating + plotting various results for all input values in relevant columns

Are you required to use VBA for this? It looks like the kind of problem that a Data table would readily solve without the need for VBA. If you are unfamiliar with data tables: https://www.excel-easy.com/examples/data-tables.html

Steps I took:
1) A data table is going to want only one input rather than two. I can reduce the two inputs to one input, if I add a column of row numbers immediately adjacent to the desired output columns and use an INDEX() function in the data table I/O cells. I select column F and insert a column.
2) Fill this new column F with row numbers. In F2:F5 I enter 1, 2, 3, 4. Then select F2:F5, grab the little + at the lower right, and drag down to fill the column with the numbers 1 to 304.
3) I need a row number "input cell" over by the Poisson table. I choose to use J27 for this input cell, and enter 1 in J27.
4) J26 and K26 need to get the desired input values from columns B and E based on the row number in J27, so I enter an INDEX() function in each. J26 =INDEX($B$2:$B$305,$J$26). K26 =INDEX($E$2:$E$305,$J$26).
5) I need a simple formula at the top of the output so that the data table will know what the output cells are. I replace the 1 in G1 with =M$26 and copy that into H1:I1. (If you want to keep the 1, 2, 3, insert a row below the 1, 2, 3 and enter these formulas into the new row 2).
6) Now I am ready to invoke the data table command. Select G1:I305 (G2:I306 if you inserted a row) -> Call the Data table command -> column input is J27 (or J28 if you added a row) -> OK. columns G:I should fill in with the appropriate outputs based on the different inputs. One advantage is that data tables will autocalculate with each calculate event, so the data table will calculate automatically if any of your input data changes.

Hopefully I explained that all correctly. If not, the basic idea should still work (fixing any errors in references and such that I made). Are you required to use VBA? Will something like this work for you?

I've followed your instructions but every time I try to create the data table excels says "Reference to input field is invalid".

Not sure why you are getting the error. It seems to work fine for me. Did you change something a little (a different "column input cell" or used a different column for the index numbers or something)? Something different in your newer version of Excel? Are you certain you followed all the steps? Can you upload a new sample with what you could get to work? My guess is that something is slightly different so that Excel cannot correctly link the column input cell to the correct column in the data table or Excel cannot link the output cells to the correct columns in the data table.

In the real scenario the input values are only in every 82nd row and the results should be presented in columns F:H but 2 rows below the row that includes the input values for this calculation.

I guess if you want to insist on using VBA we can go that direction. However, I would still be inclined to use a data table like this. In this scenario, where the inputs are spread out, I would build a consolidated table from the sparse data. Then set up the data table. Finally, the output cells can pull their results from the consolidated data table. Using your sample sheet as a template and assuming we can figure out why you are having trouble getting the actual data table to work, the only additional changes that would be needed would be:

1) Columns B and E in the sample sheet/consolidated table template would need INDEX() or other lookup function to pull the data from every 82nd row of the main sheet. Details depend on exactly what you mean by "every 82nd' row. For example, if you mean rows 82, 164, 246, etc., then this INDEX() function could be something like =INDEX(main!B:B,$F2*82) in B2. Copy into column E (and adapt references, if necessary).
2) The output cells (every 82nd row but 2 rows below the input cells) in the main sheet would need INDEX() or other lookup functions to pull the results columns G, H, and I of the consolidated data table. If there is a convenient index number somewhere in the 82 row block that an INDEX() function could reference, this could be as simple as =INDEX(datatable!G$2:I$305,referencetoindexnumber). With appropriate relative and absolute references, you may be able to simply copy this into all of the output cells (every 82nd row 2 rows below the input cells).

I don't know how far to encourage this non-VBA solution -- especially if you are absolutely certain that you would prefer to use VBA over native spreadsheet functionality. Are interested in pursuing this kind of non-VBA solution? (I would note that VBA is going to need to do most of the same tasks -- it's really just a difference in programming language, if you want to think of it like that. It's not like VBA will necessarily be easier or faster. Unless you find programming in VBA easier than native spreadsheet functions).

Yes, I did mean J27 in both. Good catch.

It looks like it is all ready to add the data table. In this latest file I A) Select F1:I305 (I had G1:I305 in my previous instructions, so maybe that was the mistake) then B) Data -> What if analysis -> Data table -> enter J27 in the column input cell field -> Okay. The data table populates with all the results.

It looks like you entered J27 as the row input cell rather than the column input cell. Select F1:I305 again, create the data table, and put J27 in the column input cell field.

A data table cannot be spread out to be in every 82nd row. It must be a contiguous range. My idea is to pull the data from the main sheet where the data is spread out into this sheet where the data is in a single block, then pull the result back into the main sheet where things are spread out. So this should not delete any data, just make a copy of the data for the data table to work with.

I've tried to illustrate in the attached. I don't really know what your main spreadsheet looks like, but I have tried to show something where the input data is in every 82nd row (starting in row 82). Formulas in B and E of Before pull the input data into the data table. Then I have formulas in main that pull the results back into main (2 rows below and to the right of the inputs). In practice, you would enter your input data in main, the results will automatically calculate in Before, then the results will automatically appear in main.