Hi DeadRinga,
The latest beta (available
here) allows you to define the number that PT will try to load, note though, that they consume BB internal memory, so it's not recommended to go too high (though there is an unlimited setting).
The first 50 and last 50 thing is because some podcasts publish at the end and some at the beginning, so getting half on each end ensures you have the latest episodes.
Once you bump the amount it downloads, use the 'Update and sort' menu option in the episode list (also new in this beta) to get them in the correct order.
Hope this helps.
-Marcus