That sound just awful. I'm really sorry to hear about your accident.

If you are having repeated fractures, once you are over the worst of these injuries, you should ask for a DEXA scan to check your bone density. Ideally, not just the two areas they normally scan to check for osteoporosis, you'd really want all of your bones scanned to give a more accurate picture of what state your whole skeleton is in. After that I guess you have to take advice about what if anything else is open to you by way of treatment.

However, if you are going to be stuck with brittle bones and there are no interventions that make a difference, it may be a question of managing your lifestyle to minimise the risks of further fractures. In the UK most hospitals have 'falls clinics'. I don't know if they have these where you are. Typically they are aimed at elderly people to help them to minimise their risk of falls and to teach them how to fall in a way likely to cause the least amount of damage.

Since you already have CRPS, I'm not sure I can see what benefit is gained from splinting or using a boot rather than a cast. It is still designed to immobilise a limb, you say it is taking twice as long and it is exposing you to increased acute pain. The longer immobilisation and increased acute pain are both things that are believed to contribute to the development of CRPS so I don't really see how that is better than a shorter time in a cast with less pain.

Ideally you would commence a course of vitamin C right away and continue this for at least 50 days. This simple and cheap intervention has been shown in several clinical trials to be effective in reducing the rates of CRPS in various types of fracture and other injury. Some trials used 500mg per day and some 1000mg. Either amount is completely safe and at these levels your body will simply excrete what it doesn't use.

Other than that, I'm afraid I can't suggest anything else except to make sure your doctor reviews your pain relief during this time when you are suffering this additional acute pain to make sure you are as comfortable as possible.