That's a really good idea. Put the broken end in a drill press and carefully center a hole. Then screw it in and continue the hole.

I'm currently waiting on parts to do my timing belt right now on my MIVEC DOHC V6 so I understand the space constraints you're dealing with. I previously had a 3.8 crank bolt (on my wife's gen3) come apart on the highway a long way from home due to an improperly torqued/dealer installed crank bolt, with catastrophic results. The shop it was towed to (too far from home for it to be worth it to do it myself) used an insert on the crank, and was able to properly torque a new bolt in there. Its been good for three years now, and about 50k kms, so it can be done successfully.

I think so far you are going about it the right way. Good luck.

Phil