Starting a daycare, especially at this age is a huge life change for them. My son was just about couple of months younger than yours when he started and I remember the hell we went through. So, I feel for you.
It can take up to a month for him to be comfortable there. Is he in an infant class or a toddler class? How does he do after the 10 minutes period?
If this is the first time you are separating from him, you really need to be very sensitive to him and responsive to him when you are around. The bedtime issues are normal and you need patient to deal with it. I'm afraid, letting him deal with it, made things worse.
See, from his perspective, you suddenly disappear and he doesn't know when or if you will be back. What can you do?
First, in the daycare. Never ever sneak out. Seek help from the staff there to get into a routine. Drop him off and pick him up at about the same time. Have the drop off routine. Hand him over to a teacher who will give him breakfast or something, give him hug and kiss, tell him you will be back after the nap. And leave.
And keep your word.
At the bedtime, I wouldn't leave him to cry one moment at this stage. Do PU/PD or WI/WO, but let him know that you are there for him. And again don't sneak out. Come up with a plan and stick to it. If you need more help with dealing with the bed time, feel free to post in the Toddler Sleep board. Ladies there have tons of experience and advice.