Actually, from the email you included in your post, it appears a "reason" was given to you; it also appears that you don't understand the basis for that reason.
I wouldn't be focusing on how your content might have been "illegal" or a violation of the TOS. Other than the "proxies", I don't see anything at all in the Dreamhost Abuse Department's response to you that indicates there was anything wrong with the content on your account.
According to what they have told you, "suspected fraud", "multiple accounts", and "running web proxies" are what concerned them enough to suspend your account; I suggest those are the things you should be trying to sort out with them.
Right! It seems pretty obvious to the casual observer (and it has even been explained to you, in writing!) that whatever "issue", or issues, you had are not "cleared".
You might consider that, if there were identification issues (including valid addresses, names on charge cards, multiple accounts using the same email address for the primary contact, etc.) their lack of confidence that you are who you say you are may well be a big part of the problem.
That said, I think you might get further in your attempt to understand what happened and possibly get at your data again if you look at things a little more professionally and with a little more understanding of your situation:
You don't have a backup of your data? That is unfortunate, but not really DH's problem. Since you seem to not understand this, and feel you have some "legals rights to my data and files on the server", I suggest you go back and read (or read-read-carefully) the Terms of Service under which your account at DH is provided. Inferring that DH has a legal oblilgation to protect, backup, or even continue to provide you access to your "data" and "files" stored on their servers is just ignorant - the service is essentially "where is as is" in nature, and you have no legal recourse if DH loses data you stored on their servers (which can happen!). I know that is not pleasing to hear, but it is true.
Additionally, your statement that DH "just simply jump to conclusions like always?" implies that you have had a similar experience with DH before. Is that the case, or are you just throwing that out because you have read other disgruntled, unhappy, suspended, terminated users express their complaints of such behavior?
Now that is a really lame tactic, and not likely to encourage DH to help you out in this situation. Do you really think that your intimation that you might "join that group" is intimidating to DreamHost in any way, and/or will cause them to help you so that you don't "bad mouth" them on the net?
Here's a free tip when dealing with businesses that are in the public eye: They expect that that you will loudly inform everyone who will listen that you were badly treated if you feel you were treated unfairly. The fact that they suspended your account, knowing full well that you could go on the net and yell, "Dreamhost S*cks" from every venue that will have you, means they are prepared for you to do just that. This also implies they feel confident that they are doing the "right thing", and are prepared to defend themselves legally if they have to.
They have access to "really good lawyers", and a lot more money to pay those lawyers than you do...just a thought!
As for your "Conclusion":
You should have backed up your work no matter what computer system you had it on, and they did give you a "reason" - you just don't like or understand it. You should focus on getting the clarifications you desire rather than the data you failed to properly protect or claiming that, since you don't understand the "reason", no reason was given. That would be a "professional" approach likely to get you the most consideration from Dreamhost.
Read, and try to understand, the Terms of Service you agreed to. They have no obligation to "warn" you of their "fraud" concerns. That said, you do not really know what they did, or didn't do, in trying to contact you - only that they didn't succeed.
You are clearly missing the point completely here. You have not been "wronged" per the TOS; you have had your account canceled/suspended (and your money refunded). If you really, really want (need) to get at your data, I submit that you will have far better luck with that asking, politely, without threating or blustering, for them to help you with that. I don't know if they will or not; but looking at it from a "non-hostile" perspective is likely to be more productive than blustering about it on a public forum.
"Hostage" implies that they expect or desire something from you in order to "release" the data, and that does not appear to be the case here.
I've already discussed the short-sightedness of not backing up any files and "precious" databases" that were important to you; they must not have been very important or precious, or you would never have placed your only copies of same to a $10.00 a month shared-server webhosting account. That's almost as ignorant as not backing up important data from your own hard drive.
They haven't "accused" you; they refused to do business with you -and they refunded your money. Now you are just looking foolish. Call a lawyer, and pay some money, to have him/her explain the TOS to which you agreed (since you don't seem to understand it at all).
Try to find a "cheap one" to minimize the amount of money you will have to spend to learn that you have no hope of recovering from DreamHost via a lawsuit over them terminating your account and/or not providing you continued access to their servers.
Hey, who knows? Maybe they will! Dreamhost has exhibited an amazing amount of patience in dealing with people with no clue. They are lot more tolerant than I would be.
Once you published this kind of nonsense in a public forum because you got impatient with not having all your inquiries handled at the speed you would have liked after I had explained to you why I terminated your account and refunded your money, I'd be sooo done with you.
DreamHost, on the other hand, generally bends over backwards trying to help the ignorant, and they even tolerate the mean-spirited rather well - so you may still have a shot! You ought to just explain that you foolishly did not back up your data, and that it is really important to you, and beg them to tarball it up for you.
Using your "student" status to get yourself some basic training on resolving business problems might also be a good idea. Good luck - I hope that you are able to salvage your project...and that you learn something from all this.