Yeah, unfortunately there's a time limit on editing - as spammers have been able to make posts and then edit links in at a later date.
What you could do is create the article in word like jcegt87 suggested and then paste it in as a 2nd post (or just write/add to it directly in a 2nd post), once you're ready I can replace the 1st post with that information and fix it for you.
I'll see what I can do to put a longer term fix on this, as it would be helpful to have a much higher edit limit for that particular forum - but I don't know if that's possible. For now, if you add it as a 2nd post and I'll fix it all manually.
I'm sorry it's a little bit of a pain to do this, but I'm really grateful you're creating articles - it's a huge help for other members :D.