Fix too-small abbrev obarray bug with autocorrect

I'm seeing a bug here, but I'm surprised. Surely more people than just
me have run into abbrev tables being cut short because it grew past the
default obarray size?

config.org

@@ -4279,12 +4279,21 @@ too. We could just not save it, but it seems nice to get the count information.
 (defvar autocorrect-abbrev-table--saved-version 0
   "The version of `autocorrect-abbrev-table' saved to disk.")
 
+(declare-function math-next-small-prime "calc-comb")
+
 (defun autocorrect--setup-abbrevs ()
   "Setup `autocorrect-abbrev-table'.
 Also set it as a parent of `global-abbrev-table'."
   (unless autocorrect-abbrev-table
-    (setq autocorrect-abbrev-table
-          (make-abbrev-table (list :enable-function #'autocorrect--appropriate-p)))
+    (let ((obarray-default-size
+           (if (>= emacs-major-version 30)
+               4 ; In Emacs 30+ obarrays will dynamically grow.
+             (require 'calc-comb)
+             (math-next-small-prime
+              (+ (hash-table-size autocorrect-record-table) 50)))))
+      (setq autocorrect-abbrev-table
+            (make-abbrev-table
+             (list :enable-function #'autocorrect--appropriate-p))))
     (abbrev-table-put
      global-abbrev-table :parents
      (cons autocorrect-abbrev-table
@@ -4310,7 +4319,7 @@ Also set it as a parent of `global-abbrev-table'."
           (setq coding-system-for-write 'utf-8-emacs))
         (goto-char (point-min))
         (insert (format ";;-*-coding: %s;-*-\n\n" coding-system-for-write))
-        (write-region nil nil autocorrect-abbrev-file 0)))
+        (write-region nil nil autocorrect-abbrev-file)))
     (setq autocorrect-abbrev-table--saved-version
           (abbrev-table-get autocorrect-abbrev-table
                             :abbrev-table-modiff))))
@@ -4409,12 +4418,14 @@ split the actual reading and the abbrev generation into two parts though.
   "Ensure that all entries of the abbrev table are valid."
   (obarray-map
    (lambda (misspelling)
-     (when (stringp misspelling) ; Abbrev's obarrays start with a symbol
+     (setq misspelling (symbol-name misspelling))
+     (unless (string-empty-p misspelling) ; Abbrev uses an empty symbol for metadata.
        (let ((corrections (gethash misspelling autocorrect-record-table)))
          (unless (and (= (length corrections) 1)
                       (>= (cdar corrections)
                           autocorrect-count-threshold-history))
-           (define-abbrev autocorrect-abbrev-table misspelling nil)))))
+           (define-abbrev autocorrect-abbrev-table misspelling nil)
+           (unintern misspelling autocorrect-abbrev-table)))))
    autocorrect-abbrev-table))
 
 (defun autocorrect--create-history-abbrevs ()