It looks as if this landlord has probably committed multiple violations of your legal rights. It would be a good idea for you to become familiar with landlord-tenant law in MA. This seems likely to be a situation where you may be cheated out of money owed you (like the security deposit) unless you take the landlord to court. You may also be able to collect damages for his violations of your legal rights, something you might want to seriously consider as soon as you've moved out, both to help yourself be compensated for the misery this guy has caused and so he may think twice about treating future tenants this way.
In any case, as long as you still have to deal with him, even for just a few more weeks, it would be a good idea to become familiar with the basics about tenants' rights. You'll be in a much stronger position to deal with this if you know what the law says about landlords' and tenants' rights and responsibilities. Below are several addresses for websites that provide info on tenants' rights in MA. You might want to do a web search for additional sites (under "Massachusetts tenant rights," "Mass. landlord tenant law," etc.). I did research on the law when I had trouble with an unscrupulous landlady several years ago, and I discovered that few of these websites have every last bit of info, so it helps to look through a number of them, since you may find one with an important piece of information you didn't find at the others.
Massachusetts Tenant's Handbook
Tenants Rights in Massachusetts - Avvo.com
Included in the state laws about tenancy are requirements for habitability of an apartment, and these include the specification that the temperature inside the apartment must be at least 64 degrees at night and 68 during the day. Given your situation with the heat, you may want to consider contacting your local code enforcement officer to compel your landlord to do something about the heat. Even if you're willing to tough out the chilly temperatures for a few more weeks, if you think you might want to go to court it could be useful to have a record of this violation, as any incontrovertible evidence of violations committed by your landlord, like an official record of a code violation, may lend credibility to your other claims about the landlord's conduct, so you improve your chances that the judge will believe you and not the landlord.
This is a bad situation, but it's good that you'll be out of it soon. Hang in there.