Mr. Gerrit,
I went up to Omaha and back one day this summer right after I29 was closed. I took hiway 75 from Topeka to Omaha. I don't think it added over 30 minutes to the drive each way. It was a very straight road with nice wide shoulders. Only a few small towns to drive thru and not much traffic.
Some of it was 2 line, some 2 line divided. I was happy with the route and would recommend it for towing.
I'm not if some parts of 29 are still closed or not, if so a few other shorter options my exist, such as:
Staying on 29 until hiway 2 and then going down 75
Catching 36 and going to St. Joe to meet back up with 29
Again, I recommend you check state transportation websites to make sure either of the two options I listed above are open.