Custom query looking at multiple custom fields and properly sorting

Question

For the past two weeks I've been looking for a way to create a query in wordpress that returns all custom post types where a meta_key "mytype-expired" is NOT set to "yes" and then order the results by a second meta_key called "mytype-sort-order" with the highest number value coming first. If no value exists in the "mytype-sort-order" meta_key field, I want these posts to be displayed order by date (most recently added first), and all of these should be below posts that do have a value.

For example, these set of test posts:

Post 1 (from July 1st, mytype-sort-order value not set), Post 2 (from July 2nd, mytype-sort-order value not set), Post 3 (from July 3rd, mytype-sort-order value not set), Post 4 (from July 4th, mytype-sort-order value = 95), Post 5 (from July 5th, mytype-sort-order value = 90), Post 6 (from July 6th, mytype-sort-order value not set), Post 7 (from July 7th, expired="yes").

should be returned as follows:

1. Post 4 (from July 4th, mytype-sort-order value = 95)
2. Post 5 (from July 5th, mytype-sort-order value = 90)
3. Post 6 (from July 6th, mytype-sort-order value not set)
4. Post 3 (from July 3rd, mytype-sort-order value not set)
5. Post 2 (from July 2nd, mytype-sort-order value not set)
6. Post 1 (from July 1st, mytype-sort-order value not set)

(Post 7 not displayed because it's expired)

I explained my current approach of trying to use meta-query here here, but I found anything new or made any progress myself, and with no responses to my first question I'm wondering if there's another way I could accomplish this. I've been able to not return expired posts, and order by "mytype-sort-order" meta_value_num OR order by date. The problem I keep running into is I can't order by BOTH "mytype-sort-order" meta_value_num AND date Even though I've done a lot with wordpress, my experience with creating custom queries is limited. I'm totally stuck and would REALLY appreciate some ideas. Thanks!