Trying to optimize Nook HD. 98% full Internal Storage

There's just a few books that I was thinking of purchasing today or tomorrow and some of them, not necessarily all of them, will be available for Android. The memory in my tablet is over 99% full, there's 46 MB free. The new books would probably be less than 9 MB total.
I've set "Internal Storage Capacity" to 95% in the Settings in my Nook. It's warning me "Low on space NOOK® storage space is getting low". When I used an earlier version of the Logos app in the end of October 2013 it malfunctioned pretty badly when I exceeded 75% by a lot, I had "Internal Storage Capacity" set to 95% - (or actually I don't remember if it was this tablet or my other one which is the exact same model).

I've tried to Remove as many Logos books as possible, and I don't have a lot of web browser history - I just tried to go to one page and it worked (that was earlier today, before the memory got this full). I've removed unnecessary Bibles (I have 8 English Bibles in it, no NETS or any Septuagint, I have NETS in Accordance but I don't have any iPad), all Greek New Testaments but one, unnecessary image rich resources, lexicons (I just have LN left), all reverse interlinears except the Apostolic Father's which is keyed to LN. all unnecessary Church Fathers volumes. Can You give me ideas on what else to remove? I know ZIBBCOT is using 1 GB, but I don't want to remove it. I don't have any Bible Dictionaries left on this tablet.

How long will I approximately be able to keep reading on this tablet before it starts malfunctioning? Will I have to keep removing books all the time when I progress reading if read books are in some kind of cache?

I even looked carefully on which commentaries I want to have on the tablet. I did however download a few more pastoral resources even though that kind of resources are not especially necessary at this point, it's just that I don't want to keep downloading frequently so I forget about the books if I don't have them downloaded.

I don't have time to update the other tablet right now and to put other Logos resources in it, (instead I have to put some effort right now into organizing my library, and I have a lot of schoolwork in uni and it's an important day on Friday the 25th (it may have been re-scheduled to a little later, I haven't checked, but I will also be meeting almost all my friends and family this Friday-Sunday).)

I'm trying to remove as many introductory work as possible, but a few seemed really interesting.

At first I was thinking of adding reading plans - but that was when I got the memory warning. I've removed a devotional that I've tried out but didn't like that much, and added a few new ones.

Are there any particular books that are much hard to use on a tablet than a laptop?

I could remove Beginning Biblical Hebrew by Mark D. Futato as I've never intended to learn Hebrew. And also Cambridge Greek Testament: Greek Text. Perhaps all the Church Documents, Councils and Philosophers aren't necessary but I don't know which ones to remove!

Is there a way for me to see how many books I have in the tablet?