Hi Abdulallatif,
It seems this questions comes back up for discussion every once in a while
The handle setting part was fairly well addressed. The pitch or other resin-type glue - see the glue thread for a variety of recipes - holds well enough and is easily dismantled. I suppose it does dry out eventually, but regular maintenance of the weapon would probably give ample indication when it needed replacement.
The disk pommel has also come up before. Among the tulwars I own, those with sufficiently-large handle to fit my hand do not pose problems. I actually find the pommel snug and quite comfortable, it stays locked in my hand and can't slide out. This design was used for centuries so it must have been adequate within the styles of combat used. Check out Shastar-Vidiya and Gatka videos for an indication of how the tulwar might have been used.
Tulwars are some of my favourite swords, I live the overall design and the handle/pommel disk is a major component of that.
All the best,
Emanuel