Firstly I should point out that this forum is primarily a user to user forum. Folks from DreamHost do post in some threads, but this is not the best place to obtain answers directly from DreamHost, using the contact form listed below is probably the best way to obtain answers to your questions.
Having said this; I think I can help you out with a couple of your questions.
Yes, DreamHost except payment by PayPal. However, you should be aware that the 97 day guarantee does not apply to PayPal payments.
No, the price of your plan will remain the same for as long as you maintain your account and the disk space / bandwidth allocations will also remain the same.
Actually, the disk space / bandwidth allocations grow each week, it is kind of a loyalty bonus. Also, DreamHost has a history of offering any new plan improvments to existing customers.
This one I am not sure about, your best course of action would be to use the afformentioned contact form and ask DreamHost this question.
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