No, you can't move over your app purchases. The way I see it, you have three options:
1) Hard reset the phone, set up main MS account on phone as the Hotmail one, use the outlook account for email and everything else (i.e. don't sync email from Hotmail account)
2) Go to your Hotmail account and do an actual "rename" of the account, and make it an @outlook.com address. No, it won't be able to be the same outlook address you already have, unless you delete that account and wait 270 days. Hard reset the phone, and put your newly renamed account, still intact with old purchases (which may take up to 72 hours to show up I think), as the main MS account
3) Repurchase all of your apps
Edit:
4th option: You'll still have to hard reset, but you don't even have to rename your account if you don't want to. You can just add an alias to the Hotmail account, it could be outlook.com if you prefer, and then use that alias as the main MS account for the phone. It has the same password as the main account, but you wouldn't have to change a thing and can be assured everything remains the same. I'm not 100% sure how aliases work as main MS accounts on WP, but my assumption is that they just feed off of the main account, since they use the same password and all. Either way, you can use this alias to sign in with and just pretend the Hotmail.com account doesn't exist.