I would be extremely cautious about a connection like that. By "closure", do you mean ending the relationship so you can move on? If so, I would be concerned that the kind of astral work you're talking about to communicate with their deep self would strengthen the toxic bond, not end it..
Yes that is what I mean. I have to admit I tried contacting this person via meditation and strange things have been happening in my room since and my cat has even seemed scared when he's near my room at times and i've woken up at night several times feeling very uneasy and in my dreams last night I saw a figure, a man in black standing in a black void kind of and everything was static, I couldn't even see his face. Tonight I saw him again but I was only half-asleep... So I think it succeeded... and honestly as scary as those experiences i've had lately have been it's helped me to realize just how negative this person is.
I'm thinking I should probably cleanse my room now and maybe do some kind of protection-spell or something to make sure this person can never reach me again in any way?
Cleansing is good. Self-protection is good. I'd say that you shouldn't do a spell about him specifically, unless it's just a "letting go" spell, that lets you part ways. I feel like even banishing spells are tricky if you target a particular person, because you'd still be feeding a connection to him that is based on fear (potentially even making it stronger -- subconscious can be weird like that!). Stick to general intentions, like, "I cleanse myself of all unwanted negative energies", or "I protect myself from all negative influences."
My therapist taught me this visualization -- imagine that you and he are connected via a cord that goes between your navels. Reach down, unplug that cord, and let go of the end. That's what you're trying to accomplish -- to disconnect. The best way to stop feeding a toxic connection is just that -- stop feeding it.