I certainly hope he became stronger. Although up until we last saw him, he bluffed his way in both occasions you mentioned.
i hope he have become strong and not pretending to b strong
I have to admit i was impressed by his power he showed us in Impel down. He had no problems defeating plenty of guardians and even the floor beasts.
His new Mini Buggy Canon was also really awesome.
I wouldnt underestimate him too much, but he is kind of a coward.
My 2 cents (sorry for quoting myself):
I too believe he found the treasure of captain john, and he has probably used that to buy weapons or who knows what else, I noticed that his chop/chop powers work on items he holds and clothing as well as his phyical person, so with proper weaponry he may very well be able to attack in a similar manner to byakuya kuchki from bleach, just turn a seastone sword into many infinitely sharp blades and attack at once, and perhaps he has perfected his ability to move parts of himself away from attacks, meaning in the future someone may say his defenses are better than a logia class, since he can dodge any attack by moving a part of himself away, like tobi in naruto does which would make even haki ineffective.