It's a developmental phase, and they develop more gross motor skills etc. Kids learn by "repetition" they "practice" their new skills even, yes, in the crib when they are "supposed" to be sleeping. They don't do it on purpose...it's part instinct and that they are exploring. It's a natural part of development and normal.
Yes, these developmental/cognitive growth & development spurts WILL AFFECT THEIR SLEEP. It's normal. But it is a phase and it will pass.
In the meantime, well, just bear with it. BUT, by all means, KEEP his regular sleep/nap routine and sleep/nap times. Keep up with it and the consistency. When the phase passes, things will go back to normal.
Both of my kids went through this. And it WILL happen at any developmental leap and growth spurt.
The good thing here, is that your son is developing well...he is already standing/pulling up. Good for him! BUT, remember that these skills don't always happen as a "common sense" thing...ie: he can stand up....but that does NOT mean that a baby can then sit back down nicely, and then lie back down, AND put themselves back into a nice little sleep position, all by themselves, and how we want them to. Many times, they can indeed stand up/pull up...but do not yet know how to sit back down...so they will fall onto their bum and get all frustrated and then stand back up again, over and over. He is probably not yet at the stage where he is old enough to do things in a sequence: ie: stand up, then sit down, and then lie down to go back to sleep. His "new" skills are still throwing him off...but he WILL adjust and then he will learn to do it. But you must give it time.
So, you will need to either (1) let him cry it out and leave him there standing in the crib all night until he gets too worn out or (2) go in, help him & put him back into a sleep position, then pat him, and leave the room. In either case, it WILL interrupt his and your sleep.
It's not easy for them either... they have a lot to adjust to and need to "learn" coordination and how to handle their bodies and new skills.
Remember, that it is a growth phase and is normal. BUT any "new" sleep/nap habit you introduce now, can and may alter his regular sleep/nap habits. Main thing is you want them to feel comforted at this stage of changing development...so be there for him, but encourage him to self soothe too.
When my kids went through these things, I would go in and adjust them, help them, even if it meant doing it several times during the night... but I would leave them in their crib...pat them, comfort them with my voice, etc., but I did not take them out. ONLY if they were really distressed, would I then take them out, and then (because I was so tired) I would co-sleep with them. BUT initially, I always put them down in their crib first... and then went from there.
It's a phase though. But, once at around 6 months old, when my son was crawling and doing it in the crib too and it affected his sleep, I was so tired...so I would sleep with him as this was the only thing at the time that got him to sleep....BUT THEN, thereafter, that is the way he "expected" to fall asleep, and I had a hard time getting him back into the crib. It took a lot of effort to get him back into his crib. But he finally did.
Anyway, I'm rambling so I better stop here. Hope this helps...your boy is normal and developing. I know it's not easy...but it will pass. All the best,
~Susan