Is it possible to know with say a reed-Solomon technique how many paity bits I would need to add to each block to move in the neighborhoos of 100%?
Normally yes, if you know that you will never have more than $e$ bit errors in a block of length $N$, then you could design a RS code that would fix them all. The problem in your case is that 30% bit errors is a LOT of errors. Assuming the errors are randomly distributed, no RS code will be able to fix that many errors. The number of parity symbols you would need would exceed $N$.
The analysis goes as follows- RS codes work on symbols, not bits. All of the RS codes that I have seen have symbol widths of 6 to 9 bits, with the most common symbol width being 8 (CD's use an 8-bit wide RS code). At 30% bit errors, well over half of the symbols will have errors. You need two parity symbols for each error that you want to correct, so when over half of the symbols have errors it is impossible to correct them.
You may think "why not make the symbols narrower, reducing the chance that they will contain a bit error?" The problem is that the block length, $N$, is $2^m-1$, where $m$ is the RS symbol width. If you reduce the symbol width to 1, then your block length is 1 and you can't correct any data. Thus, no RS code can correct your errors.
I would say that your best bet is a low-rate Turbo code, though turbo codes cannot guarantee that they will fix your errors.