Team lead is playing politics. He would be happy to see you gone. His strategy is to grind you down till you run out of energy and motivation.
Do not tolerate this. Do not let someone else take the victory lap for your hard work.
The bad news: This is going to happen in your career often. If you are good at what you do, you become a target. Get used to dealing with it.
The good news: his playbook is well known. Heres what you do: Go to amazon and buy ten books on office politics. Then take a week of and read them, and mark out the behaviors you see. Finally schedule a meeting with the founders, and explain to them what you are seeing.
Then everytime he behaves like an a-hole, call him out. Put in email and send it to the co-founders. Sunlight is a good disinfectant. These people are usually cowards and they FEAR the truth being known by the key stakeholders - that they are not good at what they do so they compensate by messing with the people are good, and they have a lot of experience doing it.
Stop being nice to team lead. You are at war with him. He wants you out. Your rational response is to get him fired as soon as possible. Its either him or you. Or demand that they make you a team lead too. Make a huge fuss about this.
But PLEASE, if you go down, go down fighting. Don't let this MF win.
Being loud and blustery won't make anyone happy with you, and playing politics well is all about having powerful allies. The lead has probably been slandering you to the founders for the last several months. Go talk to them, but think about whether they are more likely to listen to someone who sounds happy and interested in making a couple changes, or to someone angrily ranting.
Honestly, your manager controls what the founders will hear about you, so unless everyone on the team is having problems with him, you just don't have much control over your situation here. So reduce your work output, take time off, gently bring up the issues with the founders, wait a few weeks, and then quit.
If you like email me at fairwork@gmx.net happy to share stories. (or anyone else reading this in this situation where you are doing all the work but getting screwed over by incompetent politician manager).
Clearly you've never been in this situation. Some people go through life not knowing these behaviors, and one day your company will fail because you didnt see this happening below you.