I'm not a speech therapist or anything like that, but I'm a father of a 4 year old with an autism spectrum disorder. So, take my words with a grain of salt.
Regarding speech, I think the most important thing is being patient. No rush, avoid putting the kid under any kind of pressure. I'm saying this as someone who had done the opposite and is now sure it only made things worse. But you should probably try different approaches. Some prefer highly structured approaches, like ABA. I hate ABA because it's like training a dog. Besides, it made no positive impact on my child (it was probably negative). Yes, she did learn a couple of new words, but she doesn't use any of them in the "real world". Every single word she uses actively she learned while playing, exploring, listening to us, you know, doing all the small, everyday things. Also, I too have a book recommendation -- I have just read "It Takes Two To Talk" (look it up on Amazon -- unfortunately it doesn't appear to have the "look/search inside" functionality available. I can give you some more details when I get back home, email me if you're interested) and I suggest you to take a look. It's very simple, practical and essentially, common sense (most of the other books on the topic I've read aren't exactly like that). But it'll save you so much time. You'll be up to speed in two days, instead of, say, 6 months. There's another book on the same topic I heard was great, but the title escapes me right now :( I ordered it a couple of days ago, so I guess I'm going to know the title again really soon :)
Regarding potty training, what worked for us is: first, it's absolutely crucial the kid is at home all the time for this to work. So, no kindergarten. Second, whatever your specific approach is (I suggest you watch the kid's body signs and always have the potty available :), do it for one week. If it doesn't work, stop. Wait for a month or two, then try again (possibly using some other approach). When the kid is ready it'll just happen.
Please keep in mind that I'm no childcare professional. Also, there are many conflicting approaches. For example, I'm sure someone will tell you, for example, that ABA is great. And maybe it really is, for some kids. I guess you'll have to experiment a lot. Good luck! And don't rush. Just don't rush.