I knew it was a long shot
I have not found 155F to be uncommonly high especially for a malt-forward beer containing no carapils (or other body/head enhancing additions). As an example, I recently did an ESB mashed at 157 for 60 minutes with a 10 minute mashout and it fermented to completion within 5 days or so (SG 1.058, FG 1.015).
A longer mash actually gives the enzymes more time to work on breaking down the sugars, thus making a more fermentable wort, which should yield a lower final gravity.
Based on the information you've provided, I have not come up with a reason why you would be stalled at 1.030 with the possible exception of "the yeast just crapped out due to temperature drop". If you're willing to throw more money at this batch then you could picked a vigorous liquid yeast strain, make a 1L starter, and pitch it at high krausen with starter-to-beer temperatures very close to each other (~70F for each). This should give the yeast the best chance of just going from eating the starter sugars right into eating the beer sugars, and if the temperatures match then there really should be no acclimation or lag phase.
I personally would not bottle that batch for several reasons: possible bottle bombs, high residual sugars, low alcohol. If I was in your situation and was unwilling to put more money into the batch I would either wait indefinitely for the batch to finish (1-6 months) with what's already in the ferementer; try to encourage it to finish up by pitching a starter at high krausen; or dump it if nothing ever worked.
Edit: I just had another idea about your hydrometer reading. Are you giving the hydrometer sample enough time to dissipate co2 and let sediment settle? It could be as simple as pouring your sample through a coffee filter and letting it sit for 12 hours on your counter prior to taking a reading. High levels of either of these will increase the gravity reading.