To answer your first question, the solo 401(k) is a qualified plan. The contributions are based on a percentage of self-employment income. If you are no longer earning income as a consultant, no further contributions can be made. You can, however, leave the money in the plan to grow tax-deferred.
The loan provision is still in effect and you would be able to borrow up to 50% of the balance if it's less than $50,000 (I'm pretty sure about that limit, but you can check with your plan administrator).

I'm not sure I understand the question about the rollover. You say "previous 401k into one larger Solo 401k" after you end self-employment. I know you would be able to roll your Solo 401(k) into your new 401(k) plan at your previous client's company. I'm not sure about vice versa since you would technically be "separated from service".

Check with your plan administrator for confirmation on all the details. They will be able to answer the questions more in depth.

Ron, ChFC