Firstly, I should point out that this forum is primarily a customer to customer forum. If you want answers directly from DreamHost you should use the contact form linked below;
Having said this, I will do my best to answer your questions.
Yes, you can have 'unlimited' MySQL databases, up to the storage limits of your plan.
Yes, both Telnet and SSH access are available.
You can host an unlimited number of domains with all the DreamHost shared hosting plans.
If you are currently managing with 2GB/30GB, I suggest you try the level 1 plan, which provides 200GB of storage and 2TB of traffic.
Sorry, but I do not know the answers to your other MySQL questions. I suggest you ask these questions directly of DreamHost using the contact form linked above.
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