I think you need to take the house off the table. You guys do not sound like you are ready for it...at least not THAT house...maybe one that costs less money.
If you are having to work so many jobs to make the house possible...you will continue to have to work that many jobs to keep the house running. There are expenses out the ying yang when you buy a house...and $800 won't fix it...a new hot water heater...the air conditioner goes out...the sewer system backs up into the bathroom...a water leak...the oven breaks...the huge big ticket items hit you when you least expect it.
So if him putting $800 on the credit card is totally un-payable...then drop the house for the moment.
Then there is the separate issue of him sneaking around and buying stuff you can't afford.
You need to sit down together and go over your finances (and look at them with out all of your jobs, because girl you are going to burn yourself out going and going like you are)....plan a budget with a savings for your down payment on a future house. Check out a Dave Ramsey book or two from the library. He can and will tell you how to improve your credit. Not that he suggests using it at all other than for a home purchase.
If you need financial counseling...go get some...learn how it all works...have someone else explain to your husband how credit works and what it will take to buy a home. A lot of churches will offer this for free. One of my friend's husband is a financial planner and he volunteers at their church to help couples get their finances in order.
On the Minera...I hated mine with a passion...I had it removed and we use other birth control now...Nuvaring worked well for me. But I am thinking you are so stressed out and tired right now for sex to be appealing...and angry with your husband to boot.
Send the tools back...if he doesn't need them for his job RIGHT NOW...then they can wait until he does need them if he becomes a mechanic.
This is not un-fixable...we all have times where we are irresponsible with money...most of us learn and get it out of our system in our teens or early twenties. I don't see this as a deal breaker but a huge eye opener that things need to change...and if you guys work TOGETHER to make it change...then other parts of your marriage will fall in a better place.
Sending you a huge hug because dealing with our spouses weaknesses is never pleasant but his is fixable...work together to fix it.