Safe to use this combo?

When in doubt, try testing it on a hulk.

Tamiya clear in spray can, is laquer.  Panel line accent is enamel.  I have used them together successfully many times.

Just get some washes made by Flory Models.  Those are all water/clay-based and you remove the excess with sponges/q-tips/brushes dampened with water.   100% safe for all finishes.  The stuff is an absolute joy to use.  You also don't have to worry about getting it precisely in each of your panel lines, you just slop the stuff on the whole model with a big brush, wait 30 minutes, and then mop up the excess until you get the look you want.

If you used the same clear this time as the one you burned through, I would suspect any enamel reducer/thinner would do the same thing this go around.

I would think the panel liner would lift the clear.  Consider an acrylic coat like Future.