Hi Kager! Your situation is so similar to that of my closest girlfriend. She dated her recent ex boyfriend for 5 years before they broke up. They also had a long distance aspect to their relationship for 3 years. He was not as responsible with his finances and had a lot of debt. However, they decided to purchase her ring on a payment/layaway type plan. Now the problem here is that my girlfriend was very impatient and wanted them to get married since they'd been talking about it forever. She also wanted a really expensive ring ($10,000) and of course, he wasn't in any position to afford that. Still, he went with the plan. Because of all his debts etc, he wasn't able to pay off the ring as fast as she wanted and the frustration and his financial situation got to her, and really damaged their relationship. They broke up and he still had half the balance of the ring to pay off. Needless to say he never got the ring for her. I will say to you what I said to my girlfriend during that time. She's very hardheaded and stubborn, and so she didn't take my advice.
Most women want a beautiful engagement ring, but what's more beautiful is the sentimental value of the ring. At this time, your man is not in the optimal position to afford a ring for you, at least not what you want (it sound like). Financial arguments/strain is daunting on a relationship, so you need to address that issue first. THe best thing right now is to talk about his financial situation, and help him with a plan. Since you guys are planning on marriage, this is a great time to be open about financial standing. Take a look at his expenses against his income, and you may find ways he can cut back, and put some money towards the ring. Also, am not sure if you are determined to get a particular ring, but another option might be to get something less expensive, and you can upgrade later. The ring is just one expense, the wedding is another. You spoke about him not having the money for the wedding, is the plan for him to pay for the entire event, or did you mean he can't afford his portion? Maybe you can get some family help and you guys can pay them back. I honestly don't think this is the best time to talk to him about alternate options if his financial situation is the strain you present. If he's like my girlfriends bf, he loves you dearly and would probably opt for a plan to please you, and also for that whole male ego thing. The problem with that is that he'll be taking on an additional expense that he may not be able to afford right now, and there could be some resentment issues.
I certainly understand your frustration, but sit down with your man and try to get the finances under control, then you can determine a plan for purchasing the ring.