I'm in the process of installing a tile shower drain and have been very careful about the sloped pre-mortar base with a 40-mil shower pan liner over it and a two-piece cast iron drain. However, before doing the final tiling I did some more reading and now I'm super paranoid about the weep holes. Some caulk got into the holes, so before putting the second mortar bed down, I ran a 1/8" drill bit through the holes. I added a bunch of pebbles before mortaring, but I didn't cover the pebbles with anything that would prevent mortar from seeping in. Only now that it's dry am I reading horror stories about clogged weep holes. My question is this: Is it possible to just "make sure" the holes are clear by drilling with a 1/4" masonry bit all the way through the mortar bed at a 45-degree angle to the drain and then drilling through the wall of the drain with a metal bit? I'm pretty confident I can do so without missing and drilling through the pan liner. But is it a problem to have three 1/4" holes all the way through my mortar bed? If so, could I just pack the top of the hole with a little more mortar?

I peeled up three layers of vinyl tile to find a single layer of ceramic tile. It's covered with adhesive, quite ugly, and seems to be pretty solid (no cracks or soft spots). I am planning to install ceramic tile. Can I tile over tile with any success?