As for the company reference, a lot of large companies do nothing more than issue a letter saying you worked there from X to Y date. Employment references seem more relevant when provided by an individual, so is there an individual at your former employer's business that might be able to provide you with a good reference if ever required in the future (perhaps by phone or something, rather than on company letterhead) ?
I would make it known to the new employer you are going to work for that your former employer is giving you a very hard time over this - odds are they will be supportive and it might help deal with the reference issue. Also, don't forget if things go well in your new job, then they will become your primary reference in the future.
Final thing that you might like to tell your outgoing employer ... is that there are lots of websites where people post comments about their experiences working for various parties and if they want to continue to take the current approach, you'll name and shame them publicly - that will do long term damage to their reputation. Not the ideal way to go, but there comes a time where you have to start fighting back a bit and not just tolerate it while silently counting down your final days. If things get bad, then there's also the option of going to your doctor and going out on stress leave for a week or two