Displaying all would result in problems sooner or later.
being ~112 KiB . At that rate, the Feedburner feed would stop updating around the 340th post,
when the Original Feed reaches 1 MiB.
But Wordpress doesn't normally even allow setting the number of posts in a feed to more than 50.
You should consider replacing the few base64 embedded images in some of your posts
with properly uploaded ones, even though they are quite small, 7 to 8 KiB each.
Of course you (and subscribers of your blog) could use a feed aggregator service or app that
caches old entries, instead of only showing ones that are available in your live feed.