I have had a similar issue where I had relatinships set up across several tables but there was no relation between others. In some instances I have found this doesn't matter, but in others I have had the same problem with visulisations not working.
One of the things I tried where I need just one field from anohter table was to add a new column to a second table that simple looked up the value from the first table. Then I had tables 2 and 3 with reltationships that worked and i would work around getting the data from the 1st table. This worked well for me because it was only one field that I needed to duplicate. It might be more problematic if there are lots of fields you are hoping to 'duplicate'.
If there a link between your tables 1 and 3 that you could include or superficially generate by the using the above method in some way? Like I say, I have found it depends on the fields you are looking at. Sometimes I had no issue and other times I had to work around it by adding in a field that would replicate what I was after.
i've just had a lok at your other thread - have you figured out which field is causing the problem?
I would create a table with a field from table 1 and then gradually adding in more fields from the other table. If you find some fields can be added that is probably good news at least, or are you finding that you get problems as soon as you add fields from the 2nd table?