Unfortunately, app, iBooks, music and other similar purchases are very much tied to a particular Apple ID, and it is not currently (and has never been in the past) possible to merge accounts.
Are you aware you can request a new password or change the email and/or the Apple ID now if it's only access to the email that you have lost?
Your proposal to start new and buy is obviously doable if you don't mind losing the history and all use of the past purchases.
Should you ever recover / remember / reset the past account, you would then have two accounts to enter to get both sets of content loaded. So, you can have up to 5 accounts on each iOS device, but it's a bit of a pain to keep both passwords, switch back and forth and remember which account should buy new content. (You can remove payment from the one you don't want to buy to mitigate that one confusion). I would strongly recommend you keep working with Apple support to get your old account password reset and then change the email to match your current email / password rather than starting new.
You can also read up on how some other people solved this issue: